I own a Kyro II (Hercules 3D Prophet 4500) and a Turtle Beach Santa Cruz card. I have been very happy with both products so far. If you want to see all my system specs, click on the rig link in my sig. Anyway, here's my impressions of these two products:
Kyro II: Great overall card for the money. Won't give you top-notch performance, but won't hurt your wallet either. Excellent 2D quality (60Hz. refresh rate never looked so good), good DVD playback, and excellent performance. UT plays at 70fps at 1024x768 with 2X FSAA turned on!! Good driver support from Hercules and PowerVR, constantly fixing bugs as soon as they are found. It does have problems with some games as previously mentioned, but this is a new card and given Hercules' track record I know these problems will be fixed with time. Overall, you won't get the performance of a GF2 Pro or Ultra card, but you won't pay for it either.
Santa Cruz: Excellent sound card! Take my advice and buy this card over the Philips Acoustic Edge. Both cards cost about the same, but the Santa Cruz card is much better. Great sound in all my games, MP3s, and DVDs. I currently have it hooked up to a set of Boston Acoustics Digital BA790 speakers using the Versa Jack for digital output and it sounds great! Definitely worth the $75 + shipping I paid for it at outpost.com. It even has support for up to 6 speakers, which means I can hook up my old set of Altec Lansing speakers once I find the time to dig them out of the closet. The Philips card has incredibly buggy drivers, especially under Win2K and IMO it doesn't sound quite as clear as the Santa Cruz. It also tends to take up more CPU time. Overall, a great sound card if you're willing to spend the money.
There you go! Hope this helps!
Nick