Rabanni,
I always built my own computers (never was a Mac guy) but got tired of it and purchased a gateway 2 years ago. Went a bit overboard spending $5,000 (it is a screamer) but I do photography so wanted the fastest available (CPU, HD and RAM) so went for the fastest I could find. You don't need to get that crazy. I absolutely HATE HP and most other commercial brands - they think loading up your hard drive with (nonsense) software is good while it only kills your operating system (in speed, boot up, etc)performance. I went with Vista OS. Would probably go windows 7 today. I have had a few Dells and as long as they followed my specs when they were built, I have not had any issues. (I would have gotten a Dell instead of the Gateway but they insisted in selling me a Blu Ray drive, which I did not want--gotta have it my way). I have no experience with IBM. Key is specs, no OEM products, licensed operating system, fast Intel CPU (try to get the latest), I like 10,000 RPM hard drives (in a RAID array suits me) and good ram (CORSAIR, etc). I don't need a good sound card as I use firewire out, so I don't have a spec for that. (I did go with a top shelf graphics card, though, for the photograpy). I'm a little fussy with my puter so I may not be the guy to ask. I'm sure you can get something very suitable for PC audio without spending that much money, in fact, I know you can.