How much space do you need, and for that type of data?
For the OS and program drive, you need 32gb plus program room. 64gb-80gb as a starter, and up to 160gb.
For this, you want primarily fast random read and write of small blocks, since that is what the OS does much of.
The SSD is matchless in the read part, but most SSD's struggle with overload on random writes. Among the MLC( much cheaper than SLC) drives, the Intel X25-M is the only one that seems to be issue free. That is changing, as cache is added to buffer writes, and ssd's become cheaper. We might see major advances by the end of the year. Waiting on a SSD would be good for the value concious. As a early adopter I have two X25-m's in raid-0, and they are performing well. I initially got one, but it was not big enough. I tried to sell it on e-bay, and go back to my velociraptor, but could not get my price. I came across a secone one at a good price so I got it. Primarily so I could get a single 160gb image for my OS, applications, and data.
At $300 each, they are pricey.
The velociraptor is a very good drive. From experience, it is quiet, cool, and fast. Here is a link to some benchmarks comparing it to other drives, including 15k server drives. It is second only to a fast SSD:
http://www.storagereview.com/php/benchmark/bench_sort.php
It is priced about $200
The WD caviar black 1tb drive is a very good solution also. The fastest 10% of the drive is close to the velociraptor in performance.
At $100 it is a bargain performance drive, particularly if you only use the fastest 10% for high performance needs.
What to get?
If your os and all your live data will fit on a single fast drive, go that way if you can. I find managing multiple drives to be a pain, except for backup.
If you will have large amounts of data, like video files, then get a fast OS drive, and one or more 1tb drives for storage.
There is generally no real world(vs. synthetic transfer rate benchmarks) performance advantage to raid of any kind.
Go to www.storagereview.com at this link:
http://faq.storagereview.com/tiki-index.php?page=SingleDriveVsRaid0
There are some specific applications that will benefit, but
gaming is not one of them. Even if you have an application which reads one input file sequentially, and writes
it out, you will perform about as well by putting the input on one drive, and the output on the other.
If you have the funds, remember a saying:
"the bitterness of the product is remembered long after the sweetness of the price is forgotten"
Hope this helps.