The new gen Seagates 7200.8 (not the old 7200.7) in 200Gb and up are considered to be the best by many. Have not seen the 500 released yet, but have a 400 dedicated to my iTunes library. 5 year warranty. Awesome - meaning I installed it and haven't thought about it since
The Maxtor Maxline with 16Mb buffer also carry a 5 year warranty and has NCQ 3 which is not implemented and is certainly not necessary for audio - it is basically a technology that speeds up disk access by prioritizing the calls among multiple client accesses - ie enterprise stuff. Both the Seagate and Maxtor drives are designed for the enterprise market, and are very quiet and very fast. The Hitachis are also very good. BTW if you keep them cool - meaning a case with a decent fan - you will extend their lives
SATA is totally the way to go. I could not be happier. If you are serious and your computer will handle it, get something like the Firmtek Seritek/1SE2
External Port SATA Host Card ($95), two drives and an enclosure. Look for MacGurus.com for a lot of great background - and fear not there is stuff for the PCs.
IMHO you do not need 15,000RPM UltraSCSI for audio. Very expensive and very small capacity. Audio files are small... this is not the barrier to decent performance. A slow processor, a fragmented drive etc are more likely culprits. If you want broadcast quality video editing, then you might want to consider it but there are less expensive SATA alternatives.