Best compatible motherboard for a good price

Hey i have had my computer for 3 years now and have been upgrading it since. Of last my motherboard is playing up. i was running it on (just as out of the box) an AMD Athlon 64X2 4000+ which has been working fine up untill lately. When ever i turn my computer on after a short while (about 20 second) it powers off with no warning and does not restart. i have checked all components and they work fine so i tried a new CPU. AMD Athlon 64X2 4600+ which did exactly the same. I then tried it with the AMD Sempron 4000 and it works fine. although it works fine its not long as fast and do not have the usability of the dual core of athlon 64X2. so i was wondering what would be the best motherboard to buy that is compatible with AM2/AM2+ CPU, DDR2 800 RAM, PCIe x16 graphics card and 2X 250GB S-ATA hard drive. would be great if someone could give me a little help either for the motherboard or ever to fix my old one if possible.   many thanks
*ashlee*