It sounds like a memory error from what I can tell. I love my A7N8X-E, but I'm with Anti-Trend on that the proposed upgrade is going to do very little for you, except drain your funds.

As far as power supplies go, wattage doesn't mean much. I have an Antec 350W that's better than some 500W power supplies. The amperage on the 3.3V, 5V, and 12V rails is key. Higher amps=good, and thats what you should look at. If that's a little confusing, you want a heavy power supply, since these are using more components to give good, clean voltage. Personally, I use Antec and Sparkle power supplies, but there are some other good brands out there.

But first, I'd look into replacing the RAM. Although you should be able to get a replacement stick from Samsung, this will probably leave you with a non-working computer for a few weeks. You could always get this: http://www.newegg.com/app/ViewProduc...141-424&depa=1