Op try to find a refurbished z1 ( hp) the best thing you can get ...

Marshall
Thanks. Appreciate I would get more from a tower, it's an aesthetics thing! Do you think the screen resolution/type as shown above would be any sort of consideration in terms of running Sonar?

Both systems will run Sonar without issue - it is not particularly demanding with regard to video and they both have dedicated video cards. The Dell has a higher resolution screen so you can fit more on it, but as the screens are physically the same size,  obviously those elements will be smaller. The usefulness of this extra virtual real estate comes down to how close you will be to the screen, but as a general rule is certainly an advantage.
On the ther hand, In my studio my screens are placed a bit further back than you would sit from a computer generally to allow for the near field/mid field monitor speakers to be unimpeded so a lower resolution screen suits my purpose (everything's bigger:))
 
I have not seen Sonar on that size/resolution screen so I can't really comment beyond that. The fact that the higher resolution screen has less video ram would not be an issue at all with regards to Sonar.
 
Perhaps someone else here is running a 27" @ 2560x1440 and can comment further.
As I mentioned before I have had no experience with Dell all in ones, but can certainly vouch for the HP. They have many models and have been making them for a long time. I will say that despite the touch screen working perfectly under win 10,  I have not found it as useful as I thought. This could well be down to old habits and being very used to using a combination of mouse, keyboard and controllers though.
 
 

Also...Dell offers a Thunderbolt connection and multi touch. I called HP and they seemed to think their's only offers synaptics touch which they THINK means you cannot (for example) move two faders at once. How big a deal is the Thunderbolt vs. USB for recording audio? 
 
Thanks for all your input so far. 

I have an HP laptop now, and I can tell you my next computer will probably be a Dell and/or Microsoft Surface.  The reason is HP went to a model where past the manufacturer warranty you cannot get drivers/BIOS updates without a paid support contract.  This is highway robbery in my opinion, and I will never own another HP product as a result, unless they change their business practice.  But I will say I've never had an issue with an HP computer, and they make some nice stuff.
 
As far as multi-touch, since Windows 8 and higher, 10 point touch is supported.  If the HP only supports 2 point touch they are using an older touch sensor that they used back on their Windows 7 touchscreen machines.  That is really surprising if they do that.
 
As far as Thunderbolt, a TB interface will be lower latency than a USB 3.0 device theoretically, but really depends on manufacturer and driver.  In real world situations either one will get you less than 10ms latency which is virtually undetectable.  But given everything else you've told me about, and plus what I mentioned about HP's update policy, the Dell sounds like the winner IMO.
 
 
 
 

You might want to take a look at the cost of usb3 peripherals vs thunderbolt before you decide which direction to go. 
 
I am unaware of any change in driver support policy by hp except for servers. I have never had a paid support contract and have full acces to drivers/updates outside of warranty.

Sorry let me clarify.  HP support assistant will not work without a valid warranty or support contract, and wont even notify you of newer versions of your driver.  You can go to support.hp.com to download the drivers manually, but it's a mess.  On my envy laptop there are about 100 different models with varying components and navigating HP's website is a pain.
 
On the server side and workstation side, all updates are blocked without a valid warranty.  In all fairness though Hewlett Packard Enterpise which includes the Proliant severs Z-series workstations is a separate company from HP which is for consumer products and printers.

Thanks again all. I have gone for the HP and a Focusrite 6i6 USB...taken delivery today. The PC seems really quiet which is a bonus. The screen is gorgeous. However, it appears that touch is not working at all! Guess I'll be on to HP tech tomorrow. We will get there!

Oh no - what terrible luck Bill!
 
I am guessing you are on Win 10. If you right click on the windows start Icon on the bottom left of the screen and choose device manager>human interface devices, does HID Compliant Touch Screen show up on the list? If it does, double click on it and make sure the drivers are loaded and it is not disabled.

I have a hp touch all-in-one, 27 inch and it is very nice.  I have one of the pedestal mounted screen which works much better than a flipper on the back etc.  It works, and I got my very cheap last year.