after doing some reading through this forum i stumbled onto the DMX 6Fire, which has a true 24 bit DAC
my current soundcard is a game theater xp, which has a 20 bit DAC on it, which i believe is the exact same one as on the turtle beach
anyhoo, i was just wondering if the higher bit DAC actually makes a great improvement in sound quality
The DAC chip used is only one element that affects sound quality. As with a CD player, it is important to take into account the analogue output stage and the digital board design. I very much enjoy the Game Theater XP as it's got a decent headphone jack (for a $150 sound card) and has an overall warm and forgiving character which likely hids some of the ugly computer glare that people complain about with the Sound Blaster cards.
Planar, both music off the computer's hard disk and from the CD-ROM/DVD-ROM drive should be affected by the quality of the soundcard's DAC. Although it is true that on default settings applications like Winamp will simply take the analogue output of the CD-ROM's DAC (which is always bad), there are plug-ins available that will force the CD-ROM to send a digital stream to the soundcard's DAC.
So, to sum up, you'll have to find reviews of the separate cards altogether -- that one chip is true 24-bit might suggest better overall sound, but it isn't enough evidence on which to base a purchasing decision!