yes RAM is important, but, if you don't have a decent enough PSU it won't power all the stuff you have / try to connect to your system, but, it's your money, all i can do is make recommendations
Edit: BTW: & yes your right, there is always ebay, but, personally i would be suspicious of that PSU because it doesn't say anything about how much power it can supply on each rail, as cheaper PSUs often / always "claim" to be able to output more wattage than they actually can, i've heard of a decent 300W PSU that could power more stuff than a "generic" (PSU included with a case) or crappy PSU