Iv had (this was a year ago) a Soltek SL-85DR2+R board with Onboard Realtek ALC650 6 channel audio, 384mb DDR266, Celeron 1700mhz and Ti4200 128mb video and i used to complain how slow my system was - id play battlefield 1942 with everything on low and sound hardware acceleration on / off and every time a tank rolled past it would skip... i thought it was just the game... till i installed it on my 2nd gaming machine - a P3 600mhz EB with a geforce2 mx400 64mb, 128mb of ram and a CMedia 8738 sound card and it sadly worked better... i atacked my bios settings... reinstalled windows... updated drivers and so on... eventually i ripped the sound card out of the other machine and tried it on my main - the FPS of Battlefield nearly doubled even with everything set on high... and now i have a totally new machine (P4 2.6c / 512mb / FX5600 / Audigy 1) and i must say - decent sound cards do help and sound quality wise - the audigy holds the bass well with my Logitech Z640's compared with my onboard Soundmax sound.
One thing - my Audigy 1 has game issues... battlefield vietnam - as soon as i use napalm it repeats the sound over and over till i go to the menu... and farcry hates my sound too...