Should i buy this ?

How much you are paying for it is the real question. Also, a few notes:

The X4 955 is a good "budget" gamer/OCer these days. If the price is right, it may be a worthwhile purchase.

I wouldn't get a board that doesn't have the 990FX chipset/AM3+ socket - it allows for upgrades to Bulldozer (due out at least by the end of this year). They also allow SLI, which brings me to the GPU.

The 560Ti is a good card, but if you're looking to add a second later on, you'll need a new motherboard. Either swap boards to the AM3+ socket or move to a 6950 (comparable to 560Ti in price and performance) to allow for CrossFire.

Power supply needs to be bigger - 650W for 1x560Ti/6950 or 750W for 2x560Ti/6950. It will run on 500W, but it will be under moderate-heavy load all the time and will shorten its life.

am not going to update to bulldozer .. and am not going for sli or cf
how about this ASUS M5A78L- ?

I mean, if you're not updating this platform, I would either go with this + a better PSU or wait until Bulldozer comes out (which eliminates any impending need to upgrade).

Again, we need to know how much this is going to cost in order to get an idea of how cost effective this build is.

about 4000 Egypt pound = $670

should i get asus M5A78L that support am3+ 125w
it cost less than msi 870 g46

If it's cheaper I'd probably go with it. Asus makes good stuff so I don't think it's bottom-of-the-barrel kind of stuff.

any thing else ?