The hard drive sleds that come with the Sonata II have silicone washers. Only the P-150 and P-150 Solo have the HDD Suspension System so far. All the other Antec cases have silicone washers on all the hard drive sleds/hardpoints.
It's not as quiet as the suspension, but it's sturdier. The original P-150's suspension was only rubber bands, which snapped after time. In the P-150 Solo, the improved it by wrapping the rubber band in stretching fabric so it'll last longer.
Alright... well I'm determined with the Sonata II, now. I'm wondering, will the 450w power:
1. X2 4600+ AM2
2. x2 250GB HDD's in RAID
4. Water cooling set
5. 4GB RAM
6. Sound Audigy 2 Sound Card
7. Two optical drives
Yes. Although 1GB is the standard, 2GB still allows plenty of headroom. If you just stick with 2GB of RAM, you can upgrade in the future, and the advanatge is that prices for that same stick of RAM will probably be cheaper.