TBH sata drivers are hardly any faster than ide ones of the same speed/spec (very minimal). Raptors are faster but still nothing on high end scsi drives.
What you may want to look for is the ability on your motherboard for NCQ (native command queing) to the sata ports. NCQ means a drive can internally optimize the execution of workloads. Reordering of command ques improves performance by minimizing mechanical positioning latencies in the drive. Bascially this will make it shit hot fast

(The drive itself also has to be NCQ compatible.)
I have 2x Diamondmax plus10 300gb 16mb cache NCQ sata drives and they are lush (very quiet to)
This kind of drive is perfectly acceptable for DAW use as a program drive or a audio samples drive. The only real time you may want to consider having something faster is if you're going to have a dedicated OS drive which will need low seek times.
As for DDR2. At the moment you can only get DDR2 for intel boards. AMD are waiting to see if DDR2 latencies will infact fall as at the moment DDR2 chips are performing slower than DDR1 stuff because of high latencies. Rumour has it AMD will skip DDR2 altogether and go DDR3 for dual-core at the mid/end 05.
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