bitmit, the newbies have the best deals but its a gamble if they ship or ignore you and your coins sit in escrow for a week.
Haven't tried bitmit yet. I'll take a look at it...
i'd vote first ebay.. and you can get new hardware for cheap too
but online retailers can have pretty cheap deals too like tigerdirect or newegg
Ebay is pretty consistent. I was going to bid on 2x HD 5970's for $50 each, but forgot too...lol....The only issue with those cards was refluxing the GPU and memory modules.....Today I just got a Antec Nine Hundred case and a Silverstone 1000w Modular PSU for $20 off of Craigslist...Just missing a couple mobo standoffs and 4 modular cables, but 100% tested and fully functional PSU....
...Sorry, the flash blocked of the stats of the PSU test, but all the voltages are within specs....