Also, the card monitors power usage and won't exceed 25W without a power cable. 25W was the PCIe 2.0 max I believe.
My average power consumption is ~10W and max recorded is below 20W. The max was during benchmarking and I believe the average would be closer to 6W if benchmarking was excluded.
I believe with the 640GB drives and other large PCIe 2.0 cards you'll want a power cable if you're using a PCIe 2.0 board or to change the settings using fio-config if you are using a PCIe 3.0 board.
edit:
A bit more...These cards were designed for lots of concurrent IO. Results may differ significantly depending on workload. I formatted one half of my Duo to 80GB and the other to the stock 160GB. With benchmark tools like Atto and AS-SSD I can't say that the difference in my results is significantly different. I saw ~0.002-0.003ms decrease in access time and a couple MB/s increase elsewhere. Given the 75PB endurance of the SLC card heavy OPing probably isn't worth it except for extremely heavy use. On my 320GB MLC I did see more benefit from 20-40% OP. Not huge, but significant. Given that this card is rated at a generous, but plenty reasonable 4PB endurance I think some OP is likely a good idea.
A question I've had: the cards I have are like new, but were manufactured 4-5 years ago. I know NAND can lose a charge, but does endurance decrease with age? This is a guess, but it seems everything degrades and NAND that was at the lower end of the acceptable spec might fail sooner than expected. I know capacitors go bad, but are there other components to be aware of?