$200 - $300 to spend on CPU+Mobo+RAM combo. What do I do?

My current system specs are in my 'Member Configuration' box (or whatever) and lately the machine's video output just stops after a good solid few hours of gaming. Normally I'd attribute some failure like that to the video card, but when this happens the system's sound locks up and makes weird noises, the CPU fan stops and overall the system becomes totally unresponsive. On top of that, the system never actually shuts down because the system fans and video card fans still run and the LEDs on the fans are still on. Also hitting the reset button doesn't work, I have to do a hard restart (hold the power button a few seconds to shut off then turn back on). Because of this I have reason to believe the mobo and/or CPU are dying. Doesn't help that for a while I used to have memory reference errors on a regular basis while playing WoW (but that stopped after a while. Weird). Maybe overclocking all the components a while back finally caught up to me.

So anyways I'm looking for an upgrade to my current Mobo+CPU+RAM combo. I don't trust any of these parts right now and they could all use a good upgrade anyway. Problem is I'm not 100% sure what to go for. Most of all I want reliability and a decent amount of power without breaking the bank and both sides (Intel/AMD) seem to have pretty good options. I don't really have company loyalties, but Intel does seem to have a good rep so far, yet AMD's Phenom II series is looking like a comeback. It's a tough choice for me and I could use some advice, preview builds, and whatever else you're all willing to give.

Thanks.