1 fan? I would think that fixture would need at least 3 fans to keep it cool enough to give you decent output.
IMHO, I would stay away from anything on ebay. I would look into the TEK 8x54W T5 from reefgeek or wait another month and get the ATI Sunpower. I know a guy that got sent the ATI to test and he is loving it so far. Anything generic and from China is a waste of money IMO. The ballasts go out very quickly and the bulbs are terrible!