Sorry Vikki but I don't really like any of the case options at the 2 sites you have indicated.
Once again the link is for Scan UK but if it was my money I would be buying this chassis:
http://www.scan.co.uk/Products/Silverstone-TJ08S-uATX-aluminium-Tower-Case-silver-w-o-PSUI have built two dedicated Audio PC's into this case and it offers a lot of really useful features for this type of machine, such as the front Firewire Port & 4 USB ports. It is practically silent with 2 large 120 MM fans that give good chassis cooling without making lots of noise and in combination with the other components I have already mentioned, won't impact too greatly on live Mic. recordings. It also has a small footprint which makes it easy to re-locate if you want to do so.
The other thing to consider would be a 3rd party CPU cooler as the stock AMD ones are pretty loud. As you are not going to be overclocking this PC something like this one:
http://www.overclockers.co.uk/showproduct.php?prodid=SP-000-TQ&groupid=701&catid=57&subcat=1395 will do the trick.
Asking questions is the way we all learn and in my early days of PC Audio recording I made some pretty BIG mistakes and spent a lot of money because I didn't ask the right questions although I thought I was. The real problem with building a PC as a DAW is that unless you are a muso you don't understand what it is we are trying to achieve. The normal criteria for a gaming rig or high-end video playing PC do not really apply in this scenario where high computing power combined with as near silent operation as possible is the ultimate goal. That is why I believe my original choice of components are the right ones to go for. I have spent several small fortunes on Chassis, Graphics Cards, Sound Cards etc., before getting it right and I wouldn't wish that experience on anybody.
Of course, cost is always a factor when undertaking the task of building a new PC and choices have to be made when it comes to getting the most PC for the least outlay. With my original components the only area that I think you can save is, as you have mentioned, going for a 4 Gig RAM kit instead of the 8 Gig Kit I went for. But, and there is always a but, if you can run to the 8 Gig kit now, that will save any problems with memory compatibility in the future as getting hold of the same memory, even a couple of months down the line, can prove very difficult.
Hope this helps