Restoring my good Karma

Ok, I really like my morpheus, but when I'm after something I'm quite greedy, and thus have my maximum upload speed set kinda slow, and I tend to cancel things that are too big, but well, I don't want to be an ass like that. Considering that I'm now on cable, and should be helping. So my plan is to build a morpheus driven file server to leave on while I'm at work, and possibly while I sleep. I've got a spare K6III 350 but need a board. My plan is to make a low power and quite box. I can toss in a 30 gig HDD, and not even bother with a CD drive once it's finished because I can just use a different one from the network. My questions are these. First, would the K6III be able to handle the file serving duties well? And if so, could I set myself to be a supernode, and still expect it to work well? And lastly, what is the weakest PS I could run the whole deal on? Just HDD mobo with most likely everything but LAN integrated, and the LAN card. I've heard though that a PS of higher wattage will actually draw less current because it's more efficient? If so, can someone suggest a really quite one?