I have built 2 computers with an Xcase pwr supply.
Both were 500w, however, the first one had 2 fans, and the second one was smaller with 1 fan.
The 2 fanned pwr supply worked fine.
THe single fan also worked, but I had major problems with the system. I ended up having to RMA the mobo, and the RAM. No one thought that the pwr supply would be the culprit, everyone thought it was just a bad motherboard. Well the jury is still out on that one. I don't know what the problem actually was.
Though, I bought an Antec 350w, so when I get the new board and RAM, I won't have any doubt in the back of my mind, as to if it was the pwr supply or not.
My advice is to buy a good brand, the extra money will result in peace of mind.