The area where SSDs benefit over mechanical hdds for our purposes is primarily access times, random read speeds for small files and IOPS.

The ideal setup for a wow data drive is one with minimal access times with a good number of iops and transfer speeds for small texture files. Most SSDs will do this, but the Intel drives are still clear leaders in this respect. Some of the newer SSDs can perform better in sequential read/write situations, but these are not really important for WoW.

Raid 0 setups do not increase the number of IOPS or access times and depending on the controller and cache setup, can increase them slightly in some cases. They are very good at increasing sequential read and write speeds for all sizes of files, but less so for the smaller files than for larger ones. More importantly, they won't really improve random read/write speeds much over single drive setups.

So my recommendation would be to get an intel 80GB X-25M and try that in your system. It is likely there will be other bottlenecks also, but you can at least use this HDD in a new system you build in the future. Don't worry about using a raid setup at this stage as it will not provide much extra performance for WoW. The caveat here however is that if you are planning on using the SSD for your system drive, then a raid 0 SSD setup will be slightly faster.

Cheers