Doktor Avalanche
I get peace of mind with a worldwide support contract with a company big enough to store spares for everything in case something goes wrong.
The idea that problems only happen with of the shelf PC's, and less likely to happen with custom built is ludicrous.. 
Custom PC's have parts are that are built for mass production as well. And the motherboard parts are not organic either ;).

Companies like Dell are a nightmare to get support from and more often than not, get the job done wrong. While it might say your computer comes with a 3 year warranty, it might not be worth it in the long run if they can't get things done efficiently or correctly.
 
One of the things I like about building my own machines is that if something were to happen, that one part gets taken care of quickly. I know all the manufacturers of the parts I use are not only reliable but if there is a problem, are very quick to get a fix done.
 
If buying off the shelf works for ya, then more power to you. I don't expect everyone to know how to build their own just like I don't expect others to expect me to know how to build a house. If you don't have need for a custom built computer, that's fine as well as they typically are more expensive. I expect though that anyone doing this for a living as a business would want the best computer they could get because it's essentially the brain of the operation and the expense would be well worth it.

I used to use Seagate drives exclusively, but a few years back, they had a massive fire and ever since then their drive quality has slipped badly, and they have also dropped their older 5-year warranty, for now only a TWO-year warranty, and I have seen quite a few go bad, when that didn't used to happen.
 
So, I moved to Western Digital - Black - which is a better-built drive, with a longer warranty.  I also now purely use a SSD for any primary drive in computers I now build, and have either a single or double additional hard drive setup - which would both be non-solid state 7,200 rpm SATA III drives, and these drives would hold sample library content, and the other would hold Cakewalk Projects.
 
Another thing to consider is picking up an AMD-based system, rather than an Intel-based one.  My primary music computer happens to have a pretty speedy i7-2600k, which is still a bit pricey even now - several years post-release of it.  I did some research last week, and it turns out that per several different benchmark studies, some of the 8-core AMD FX series CPU's are both quite speedy AND quite a bit cheaper.  AMD and Micro Center have also been selling AMD CPU's with bundled discounter motherboards, so that for a total cost of around $125-$160, you can have an AMD 8-core CPU and motherboard that supports either 32 or 64 GB of memory, AND where the CPU is actually faster than my current i7 2600k.
 
I would suggest a 750 watt or better power supply, (I use 1000 watt), and get one that is modular in nature - they allow you to only plug in the power cabling needed for the number and kind of devices present in your system.
 
My primary computer also runs 2 displays (both are HDTV's, 32" and 40"), using the on-board graphics on the motherboard.  One display uses standard VGA, and the other uses HDMI.  If I felt like it, I could swap the VGA cord for a DVI to HDMI adapter, and run an HDMI cord to the 2nd display, rather than use VGA.  Performance with these configurations is plenty fine.
 
Lots of choices - I would recommend a 240-256 GB SSD drive for your applications and OS, and either a single or double combo for additional drive(s) where they are 2 TB 7,200 ROM SATA III internal drives (I suggest Western Digital Black), and you would be smart to get a pretty big external eSATA III drive, or a giant external USB 3 backup drive - as big as 4 TB, for holding backups.
 
Bob Bone
 

Jim Roseberry
BIOS settings I'm referring to are *paramount* to achieving lowest possible DPC Latency.
Off-the-shelf BIOS also don't expose parameters that allow complete control over CPU throttling.
The harder you're pushing low-latency performance, the more important the above settings

 
What BIOS settings, in particular? I've never bothered to mess with my system to lower DPC latency as it seems to be very low already, but there really isn't any setting that ASUS doesn't expose for you to change, since they target the enthusiast crowd. Perhaps I should play with it.

He's right about tweaking the BIOS settings. However in general the defaults are perfectly fine (apart from Speedstep, and HTE). But if you want to get into serious tweaking and overclocking maybe sure go for it. But really that should not be necessary for a DAW, maybe a gamers setup. Getting an extra 5% of performance out of something that is already powerful enough is next to useless. The old days it wasn't but hardware wasn't as cheap as it is now.

There's a reason off shelf PC's has a limited BIOS functionality (although you can still get off the shelf PC's with it if you want!) that is the defaults are good enough and it protects the user from screwing with their PC's. The parameters that is supplied is generally good enough, or the BIOS auto senses the right settings.

The main thing to do is to update to the latest BIOS and chipset drivers.

"Good enough" is in the eye of the beholder.  
For those pushing heavy loads at 32 and 64 sample ASIO buffer sizes, a dumbed down BIOS is *not* good enough.
A 4790k running at 4.4GHz is amazingly fast... and it runs very cool (especially with quality cooling).
It makes no sense to let the motherboard throttle that speed (significantly) down.
That's simply a waste of performance...
It's also a waste of performance to live with high DPC Latency.
It doesn't cost that much more to have a zero compromise machine.
 
ie: Let's say you're working on a dense project... and there's a breakdown in the bridge to just the bass and drums.
Then, when the chorus comes back in... there's a huge stack of background vocals (a la Queen).
This is why you want to have control over CPU throttling.
The BIOS could decide to throttle down CPU speed during the bridge section... then the huge load hits and you wind up with a dropout.  This is also why you want to disable CPU core parking in the OS.
 
If you're not working at small ASIO buffer sizes, these factors are less significant.
If you're running heavy loads at 32 or 64-sample ASIO buffer sizes, these factors are extremely important.
A custom solution is about having complete control.
 
 

Re-direct?..
 
its all very well flopping it on the table and measuring your latency :D ....but really at 800-900 Euros isn't the OP  pretty much limited to building his own?.
 
I simply see a custom PC way outside the budget for the OP (and thousands of others) so recommendations for suitable commercially available MB/BIOS would be a solid contribution to the OP and the spirit of this thread...
 
 

Jim Roseberry
"Good enough" is in the eye of the beholder.  

For those who want formula 1 cars or gamer PC's that sort of thing isn't part of their vocab..!

And this thing about having complete control... Newbies really don't need to spend all day tweaking, heaven forbid being landed with over clocking environments...

Mystic38
Re-direct?..
 
its all very well flopping it on the table and measuring your latency :D ....but really at 800-900 Euros isn't the OP  pretty much limited to building his own?.
 
I simply see a custom PC way outside the budget for the OP (and thousands of others) so recommendations for suitable commercially available MB/BIOS would be a solid contribution to the OP and the spirit of this thread...

Profit margins on mass produced assemblies are tiny. I've built maybe 1000+ PC's in my life (assembled them for Samsung) and used to build my own PC's until I realise it was far cheaper off the shelf, even after adding my own customisations. Plus if hardware went wrong there was a central point of contact, distributed contacts often meant suppliers blaming each other for each others hardware.

Sycraft
What BIOS settings, in particular? I've never bothered to mess with my system to lower DPC latency as it seems to be very low already, but there really isn't any setting that ASUS doesn't expose for you to change, since they target the enthusiast crowd. Perhaps I should play with it.

Here's a good link on getting started with DPC latency:
http://www.sweetwater.com...ng-dpc-latency-issues/

TerraSin
Here's a good link on getting started with DPC latency:
http://www.sweetwater.com...ng-dpc-latency-issues/

I have no issues on my system, I was just wondering what BIOS settings he recommends customizing. I build my own systems and as such the boards I use (an ASUS X99 Deluxe in this case) have a stupid amount of customization available. I'm just curious as to what he'd recommend changing. I don't know that I would make any changes, as I said I'm not having problems and for me stability is the most important thing, followed by gaming performance, and only then audio performance. But I'd look in to the settings and what they do and maybe test it to see what, if any, difference it makes.