Well then, as far as a CPU goes, you arent going to be doing anything that taxing, so it wont matter very much brand you get. The onyl thing that matters is the cash.
The structure of AMD is that it can, analogously, carry 2 tons of weight at a max speed of 150 mph, whereas Intel can carry 6 tons of weight at 50 mph. AMD is generally faster, while Intel genereal handles multiple processes better.
My personal experience is that the information I just gave you is 95% insignificant to the avg PC buyer. Extreme overclocking gaming nerds want AMD simply because the blow away Intel processors in terms of speed/gaming (aside from being cheaper). An AMD Athalon 64 3200+ will utterly destroy a 3.0 ghz (and most higher) Intel CPU in gaming benchmark tests. However, you don't seem to be playing any taxing games, so really what is going to decide your gameplay is your video card.
For recording, the AMD will be perfect. An Intel might be better for someone who might have programs that actually use the advantage it has over AMD in that department, and I doubt even then it would be that big of a difference.
Really what you want is the best bang for your buck chip. You don't need to make a decision based on "what can this chip do that this can't," because they can both do above and beyond what you require already. Get the AMD Athalon 64 3000+. It retails on
www.newegg.com for about 150 bucks and it will be the equivalent for recording, and better for gaming, than an Intel 3.0 ghz prescott (with 2MB cache) priced at $225.
Recording requires RAM, mostly. I recommend getting quantity over cost. Buy some Corsair Value or Mushkin ram at ~80 bucks per 1GB. Grab and extra 512 if you have the cash, as some drum programs like Drumkit From Hell require plenty of RAM to load. Buying the 200 dollar per gig ram with lower latencies is pointless for you. You wont notice a single bit of difference.
If you want the best bang-for-your-buck GFX card, grab any card from a reasonable manufacturer with the Nvidia 6600GT chipset (~160-180 dollars). It blows away its ATI counterparts even at double the memory. A 128MB 6600GT will do more than you want it to, and I recommend it because if you ever get into some of the newer games, this card will be great for it. Otherwise, go with a Radeon 9600 Pro chipset card at 128-256MB (~90). The difference between the two cards with the games you are currently playing is minimal, but in terms of potential for games like WoW and other demanding games (that you dont seem to play) the 6600GT has a really high performance ceiling. I have the Radeon and I really like it. I play what you play, and the graphics are awesome and smooth.
For sound cards, it really depends on how far you plan on going. If you are just going to make amateur, primitive, and roughed out songs, go with an M-Audio card and PC Speakers. If you are going to be doing any mixing and fine tuning of your songs, get good card, a cheap mixer, and some good powered monitors. That's expensive though, and I only recommend doing it if your only chance at getting your music heard is by producing in your bedroom because you dont have time/musicians...
Any other questions, feel free to ask. Right now you seem to be looking at spending anywhere from $800-$1000 on your new PC (minus monitor). I can narrow it down more when you reply, and even give you direct recommendations from newegg.