More than 1GB of RAM may not be a necessity. It depends on the programs he uses, the amount of FX plugins, how many tracks, etc. He should do a "heavy mix" with the system monitor running to see how much memory it's using - that'll let you know if more is needed.
In audio, the soundcard generally doesn't offload some of the CPU load like a vid card does in some video apps/games. There may be specific cards to render FX faster, but they're designed for specific software (something like Protools) - general DX or VST plugins won't know what to do with such a card. Usually, the audio card is ONLY responsible for getting sound from the analog to the digital domain. Of course, for a DAW that is of paramount importance. Quality can be had cheaply - M-
Audio Audiophile, Echo Mia, etc. are $100-180 and are good stereo PCI cards that can work in 24 bit (he'll probably want this). You can get similar offerings in external firewire and USB2.0 devices as well. Besides quality, there are the number of inputs to consider. If he does anything other than overdub a track at a time, 2 tracks may not be enough; then he'll want a 4, 8, or whatever input device. BTW - audio geeks generally avoid Creative Labs.
As for sluggishness - it COULD be memory, but I'd try 2 things first:
1) You must have a dedicated hard drive that stores audio data separate from the OS & swap file drive. Preferably on a different IDE channel as well. I'd guess that THIS is the issue.
2) He needs to set up his PC to work well. Buffers, etc. should be configured according to his audio hardware and DAW software. The PC should be optimized - clean & defragged, no extra programs or services running, etc. I have a separate DAW hardware profile & login. This allows me to boot into a non-game, non-internet environment that also needs no AV, antispyware progs, or tons of useless windows processes running.
Good luck.
