You should go for a high quality power supply that features active PFC to absorb power anomalies (slight surges, ripples, noize, brown conditions). I personally like Enermax power supplies. They strike a nice balance between price and quality. I have heard bad things about Antec power supplies, but to each his own. Since you are planning on buying TWO $500 video cards, I assume price has little influence on your buying. Having said that, I would recommend something from PCPower and Cooling. They are excellent power supplies with a premium price tag. Lately, the new modular power supplies have caught my eye. They feature molex connectors on the power supply case itself, so that poeople who have modded out cases with windows can plug only the needed amount of wires into the power supply. The reason I mention this is because I would really like the clean flexibility of the modular units, but I will not buy one because of the questionable quality on a component level.
Now, as far as RAID is concerned, what motherboard do yo have? Most current motherboards are equipped with some form of hardware raid capable of RAID 0, 1, 0+1, and JBOD. I have had good luck with on-board RAID controllers from Highpoint, Promise, and Silicon Image. It really depends on what kind of board you have.
Hard drive selection is less complicated. I always pick at least two identical drives. If you sart to mix and match you can run into problems. In the case of RAID 0 (for speed), if you pair up two drives of different capacity, the array will only allocate the smaller capacity times two. So if you use your 300GB and 80GB in a RAID 0 array, the result will be a faster 160GB array.
Now the tricky part of the whole RAID mess (at least in RAID 0) is optimizing the stripe and cluster size. This is where Puppet can most likely enlighten us. It gets fairly technical at this point. As far as I know, larger stripes and clusters will increase transfer speeds of large (ie. movies) files, but at the expense of wasted disk space and slower transfer speed for smaller files. The converse holds true for smaller cluster stripe and cluster sizes. Also, the smaller the custer size the more work the RAID controller has to do in splitting up your data (writing operations) and reassembling your data (reading operations). Personally, after trudging through several articles on the subject I decided on a middle of the road cluster and stripe size.
If you have the time there is a wealth of information with benchmarks, etc. on the web. I found www.storagereview.com to be helpful.
On my home computer I have dated hardware, but I do run RAID 0:
ASUS 87N8X Deluxe
Athlon 2100 Tbred overclocked to 200x11=2200 MHz
512MB Corsair Platinum Low Latency
435Watt Enermax Power Supply
128MB Radeon 9600XT
Two Western Digital 80GB Special Editions in RAID 0 Serial ATA on the Silicon Image Controller
Leadtek TV Tuner Card w/remote
Puppet... you work for EMC?
