I'd go with an AMD actually. I'm told that in testing they have actually performed more efficiently than Intels, and I think what I was being told (in english) is that AMD's are actually faster for-the-speed than Intels. In other words, an AMD 2800 will perform faster/more efficiently than a 2.8GHz Intel, even though they are suppossedly the same thing.
Don't bother going 64-bit unless you are absolutely crazy about 32-bit recording, mainly because there are severe limitations to 64-bit pc in recording, including: apparently no drivers to run dual monitors in 64-bit mode, and the inability to use many programs/plugins, such as Sonic Foundry and others.
the most important elements of the pc are the hard drive speed and RAM. try to get the highest HD speed possible, 10,000 RPM is great, but they're not usually very large and can be pricey. and, pack in the most RAM you can fit. 4GB (2 2GB sticks) does the trick wonderfully. With a HD that fast and that much ram, you'll probably never have a dropout. You can get by with a 7200 RPM hd just fine, but don't go any lower than 512MB of ram, even that can cause studdering on playback with enough tracks and plugins going.
i built my machine, which runs great for 24/48 and 24/96 and it is:
AMD 2800
7200 RPM, 30GB HD (for temp storage)
7200 RPM, 250GB HD (for long-term storage)
512MB RAM
450Watt power supply
graphics accelerator (for max resolution)
2 m-audio delta 1010 LT
planning on up-ing to 1 or 2 GB of RAM soon
hope this helps
