How to find compatible parts to rebuild gaming computer

[Stormydream]

Hi, I'm trying to rebuild my Asus Tek, Model # CM5570, Processor is a Pentium (r) Duel core, CPU E5300 @ 2.60ghz, Mem: 6144mb Ram, Nvidia geforce 9800gt. Currently used for gaming, mostly wow. I replaced my video card & cpu fan last year, but my computer continues to overheat and lag out, freezing up and shutting off frequently, especially during game play in raids or battle grounds. I wanted to update and rebuild into a better gaming computer. Not experienced in computers but reading up it seem's I need to replace my motherboard & my cpu perhaps? I'm interested in speed and performance and would like to keep the cost under $400 but i'm not sure what parts would be compatible with my current set up. What parts would you recommend and is there anything else I should replace while upgrading? Thanks for your time & help

 

[tiny voices]

What PSU do you have?

I would do something like this:

PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: AMD FX-6300 3.5GHz 6-Core Processor ($133.79 @ Amazon)
Motherboard: ASRock 970DE3/U3S3 ATX AM3+ Motherboard ($69.99 @ Amazon)
Memory: Mushkin Radioactive 8GB (2 x 4GB) DDR3-1600 Memory ($49.98 @ Outlet PC)
Video Card: MSI GeForce GTX 650 Ti 1GB Video Card ($129.98 @ SuperBiiz)
Total: $383.74
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-03-04 17:51 EST-0500)

 

[Stormydream]

300w > Thank you