[Mauzen]

In short, ram speed doesnt matter, as long as its the same type (ddr2/3). But faster ram often is more expensive, you could save some money by buying slower ram. And 400w will be absolutely fine for this set.

However, if you just need it for file sharing, there are things called "network drives", basically hdd's with an integrated server, so you just plug them in and got it running. You would get 500gb for about 100$, so double space for half the money.