I am all for DIY (I DIY'ed my entire setup except for my current LED lights), but almost every DIY LED lighting system I saw looks like a frankenstein project with wires and drivers hanging out all over the place. If you don't mind that type of look, go for it.
If you want a more "finished" look, I highly recommend buying an LED system, but you will be hard pressed to find anything for less than $300 for a 4' tank.
The only difference I can see between my lights are the ones on Ebay are mine are not dimmable. That feature was not available when I got mine. They appear to use the same diodes (Bridgelux 3w driven at 2w) and the same amount of whites and blues.