I got an AMD 5600x2 (Old-Winsor, Socket AM2) and some DDR2 rams, now work with the old C51G mobo,
however the northbridge of the mobo seems to have issues with the heat and cannot boot last week,
now got fixed.
Any suggestions for the mobo replacement (as I foresee the overheat would be a problem again)...
I would like to keep the Winsor CPU and DDR2 rams, AM3 Mobo cannot cope with these CPU and Rams,
so it's out. And those AM2 mobos are outdated and out of stock, so it's out. The only leaving choice seems
to be AM2+ mobos (with DDR2 DIMM). Budget - less than 80 USD
Some candidates as follow
1. Asus M4A78E-SE (790GX), AM2+, DDR2, ATI, 8-phase Power Regulator, USD 75
2. Asus M4A77 (770) USD 79
Well, IMO, the 790GX is an overkill if you're not using crossfire (dual GPU). You didn't post your whole setup, so I'll just give some scenarios as comparison. I'll be more conventional, thus not recommending any specific model. Mainly because I don't have any experience with any of the brands you've mentioned.
Do you use a graphic card? If you're only using one, the 770 would be a better option. If you use 2 GPU, then the 790GX would be your best bet. Although the IGP will be a waste, but since it's cheap, go for it.
If you intend to use the IGP, either the 790GX or a 785G would do just fine.
I personally use Biostar for the very low price, yet not so trusted brand. It hasn't failed me yet though.
All three brands you mentioned are famous for the above average prices, with MSI as the most reasonable one.
Since you had personal preference towards the Asus, go for it! Branding for me is a non-issue, but this may not be the case for you.
The full set is AMD 5600x2 (AM2), Giga C51G, KST 2G DDR2-800, MSI GTS250.
770-785G-790GX would be fine for me. Just by chance to see the Asus 790GX
at 75 USD, it seems a reasonable price to me. (other mobo with 770 is around
65-75 usd with lower spec, e.g. power regulator).
For Biostar, my friend got a 790GX last year, and unluckily, it won't boot at the first
time, haha. My favor brands would be the more trusted Asus, Giga, MSI.
Since it comes down to price in the end, that Asus 790GX with similar price as a 770 is without a doubt the best bang for the buck, so they say.
I don't know about the pricing on other countries, that's why I rarely include any price linking or recommendations, I can only give insight based on usage profile. Now that you've convinced, that's a good thing.
With only one GPU, I can get my hands on an ASRock 785G for $57 and MSI 785G for $71. But then again, it depends on where you live...