I had an Extreme GAS Blowout Explosion yesterday in response to a friend sending me a link to a Supermicro motherboard which had 2x full fat sized PCI slots.  I'd been planning on buying an external PCIe<->PCI enclosure to continue using my PCI based sound cards but as they cost as much as this new motherboard and I'd need a new motherboard to upgrade my system anyway, this seemed like a good idea.
 
I'm keeping the case, PSU, HDDs, SSD, optical drive, audio cards, peripherals and such and have ordered the following:
 
Supermicro X11SAE-F Mobo
6th Gen i7 6700, 3.4 GHz (I considered the 4GHz variant, but both the price and power consumption hikes put me off)
64GB 2133 UDIMM ECC Crucial RAM (4x 16GB sticks)
MSI Nvidia GTX 970 gfx card
 
Not exactly a 'bargain' as the above came to a bit over a grand (which is why I was wondering about whether buying a new PC was the better option), but I don't think there's anyway I'd get a pre-built with PCI slots and I also don't need to buy the external enclosure.
 
A looooooong weekend of reinstalling awaits...  I've got a retail Windows 7 64-bit Professional licence, so that's what I'll install on the 'new' machine.
 
 

64 GB of ram?!  Makes us with 16GB or less feel like mere mortals.  I salute you, sir!
 
I'm curious if those PCI slots are on their own bus (Since PCI slots on modern boards tend to be bridged. Not a problem per se, but can be an issue if you need a lot of bandwidth).
 
Keep us posted!

the AsRock H97M Pro 4 has two standard PCI sockets, although the processor socket is 1150, not 1151.
I got it for about 40 dollars in a bundle deal with an i5 4690K ($200 for the i5, $40 for the mb).
 

JonD
64 GB of ram?!  Makes us with 16GB or less feel like mere mortals.  I salute you, sir!

 
I decided to push the boat all the way out.  I think it sank :-)  Or maybe it just sailed off the edge of the world...
 

I'm curious if those PCI slots are on their own bus (Since PCI slots on modern boards tend to be bridged. Not a problem per se, but can be an issue if you need a lot of bandwidth).
 
Keep us posted!

Bridged off of PCIe I think (most everything is).  Talking of pushing the boat out, I used the M$ Media Creation tool to burn a Win 10 install DVD yesterday, so I'm going to install that with my Win 7 Pro key on the new box.
 

If you run EastWest libraries 64GB will help.
 
Most consumer priced board still have PCI slots. Gamer boards have more PCIe slots.

If you choose a motherboard with PCI slots, they're bridged into the PCIe bus via a bridge chip.
Lynx and Echo cards are particularly fussy (don't work at all with bridged PCI slots).

A Xeon processor?
 
If I went that way, I'd get a dual CPU motherboard so I could have 12 or 18 cores, or whatever.
 
I know practically nothing about Xeon stuff, is it really more suitable for audio?
 
Xeon processors are not usually unlocked in regards to the clock, are they?
 
I'm not saying you've done anything odd, I'd just ignorant and would like to be enlightened as to why you went that way.
 
I guess I'm just thinking the cost is much higher for these kinds of parts, so you may as well go for broke and get the best. 

mikedocy
the AsRock H97M Pro 4 has two standard PCI sockets, although the processor socket is 1150, not 1151.
I got it for about 40 dollars in a bundle deal with an i5 4690K ($200 for the i5, $40 for the mb).
 

That's a good deal.  I have the same board but with an i7 4790. 

Not using a Xeon processor as the board is 6th gen i-series compatible (so 6th gen i7 is what's going in it).
 
Lots of 'fun' with this Saturday morning, no post, no gfx output :-(  Ran it in a bare minimum config and the problem remains.  Ran it without any memory and I did get the correct BIOS error code beeps to indicate this.
 
I'm hoping it's a PSU issue, it needs to be SSI compliant (another way of saying eps12v I believe), and supply 1.5A to the ethernet ports.  I think mine should be OK but I'm not 100% sure.  A friend at work is going to bring one in tomorrow so I'll see if that makes any difference.

arachnaut
A Xeon processor?
 
If I went that way, I'd get a dual CPU motherboard so I could have 12 or 18 cores, or whatever.
 
I know practically nothing about Xeon stuff, is it really more suitable for audio?

There's absolutely *zero* advantage to running a Xeon CPU for DAW purposes.
In fact, you'll pay significantly more *and* take a performance hit.
 
Xeon CPUs are running a significantly slower clock-speed.
In a perfect scenario, you want high clock-speed *and* more cores.
When it comes to DSP performance, you don't want to sacrifice significant clock-speed for more cores.
 
As an example, the latest iMac with Skylake 6700k is outperforming the $4000 Mac Pro (which is using a Xeon CPU running at 3.5GHz).