Atom for servers

I am looking to set up a huge group of servers. But I don't want them to make my electric bill jump drastically. They will mainly be hosting servers and I will be renting them to clients. This is the first time I am concerning myself with servers so excuse my naive questions. First thing, which I already mentioned is that they need to be energy efficient. Second they need to be stable. Third they need to be able to stay on 24/7 without crashing. I was looking at some Intel D525 or Intel 3xx atom based boards for the bases of these servers. I will be making alot of them so I dont want to throw away money. Would these atom based system be good for my requirments? Also which of the two will be better. I know that the Intel 3xx takes less power and has worse graphics, but graphics don't really matter to me. The thing is I can not find Intel 3xx boards cheaper than Intel D525 boards. Please help me find Intel 3xx boards and remember I need to buy a lot at one time. I prefer if they are made by Intel themselves and not another company like ZOTAC. Also I don't care for wireless but if they have 2 gigabit lan ports that stelar, but 1 should be ok. Yeas I know I am asking a lot but I need help. thanks