Mobo is shot - need upgrade help

Parts that work:
Neo Antec 550W
Radeon HD 4870
1 TB seagate SATA
cd-rom



LOOKING TO UPGRADE!
my dead 775 mobo and old e6750/ddr2


So the question will be - What do I get for a new mobo/RAM/CPU?

I'm looking for cheap/effective and will work with what I have for PSU/GPU. I don't use RAID and I don't need the best technology, just something that will work with my HD 4870. I will NOT be upgrading the video card, so don't ask. I won't be using SLI/crossfire with another card.

Looking to spend ~$300-$350 to get all three upgraded as much as I can but still work with what I have.

Suggestions, thanks!