You need to look into getting a decent refurb computer from someplace like tigerdirect.ca . It will be cheaper than building it, and you really have nothing to gain in this situation by building your own.
Hell no on that rosewill PSU and case, the cheapo rosewills are utter crap. For a basic multitasking business computer an Athlon II X4 620 would be plenty as would an IGP. I would put together a build based around a 620 and a 785G board in a few minutes.