why suggesting him hd 6670?where he can get hd 7750!
The 6670 simply if he can't find the 7750 in his place. Plus its cheaper too
If you compare the 630 with the x4 980 and i3-2100, the performance increase with respect to the g630 as 100% is only 7 and 8.5% respectively. So no, his CPU will not cause any bottleneck in any significant way.
Bingo!! A high end GPU like that will definitely get bottlenecked by a G620.
Bottleneck, it very simple terms means than one component being the choke point, and not letting the other perform to its full potential. A G620 and a HD 7970 is a perfect example of this. Another opposite case example would be a i7-3770K paired with a Geforce GT 210.
On the other hand, incase of low end GPU's like the HD 6670/7750, paired with a low end CPU, like the G620, the components 'match' each other, or in other words, 'are balanced'.
PS:- I'm actually quite surprised as to how much power these cheap Intel chip provide. I mean I paid 8,000/- bucks for my C2D E8400 and now you get these chips for like less than 3,000/-. This chips are probably faster in gaming than the C2D E7xxx series!! Technology sure does increase at a rapid pace!!