HTPC Client Woes

Recently, my normally rock-solid HTPC client has been locking up and turning off every so often.  I had been thinking it was a memory issue and swapping some of the chips out and/or putting them in different slots seemed to make it work again.  This, in spite of the fact that memtest showed no issues at all.  I was beginning to think the slots themselves might be bad in the motherobard.  However, it’s still happening.  Now, I’m beginning to suspect a failing PSU, so I’m looking for some options.  That Enermax reviewed earlier this week by SPCR sounded ideal, but it’s simply not available here in the states.

I’m currently thinking about the Seasonic X-650 due to the modular cables and SPCR’s glowing review .  I definitely want quiet, efficient, and modular.  650W sounds like overkill, but it’s my understanding that you generally want to run a PSU at about 50-60% of its capacity.  A 450-500W unit would be ideal for my HTPC, it would seem that, based on the chart on this page , the Seasonic is my best bet.  Any other suggestions?  I’m also trying to find a decent price ($160 seems the going rate at reputable stores).  Newegg isn’t usually an option for me because of shipping and sales tax.