If you can find it at a good deal, go for it. I know most places are currently running out of stock for the Tahiti LE cards.
http://www.superbiiz.com/detail.php?name=AT-7870XT2&c=CJ
They have stock of it though.
Well, yeah. The Phenom II X4 does only have 4 logic cores whereas the FX 6300 has six. Although it isn't really a full hex-core processor, it does get some noticable benefits in certain usage scenarios, such as Battlefield 3. The main reason why I would still recommend the Phenom II in this scenario is that it helps to compensate the budget so you can afford a more expensive graphics card, which is where most of the gaming performance comes from in things like first-person shooters. The FX 6300 is a better CPU, if not only because it is 2 generations newer and it would be utterly shameful if they made no improvements for all that money spent in research and development. So if you can get the FX 6300 and the Radeon HD 7950 for a good deal, then go for it, but if you can't at least get a Radeon HD 7870 with it, then it might not be worth it.
I agree that 7950 phenom x4 imo is better than 7870 6300, but if he ever wanted to crossfire the 965 would be bottlenecked imo, although if hes gaming one one screen and looking up something on another the 6300 would be better since it splits tasks better.
Have you considered the new GTX 650 Ti BOOST from Nvidia? It's not as powerful as the 7870 or the 7850, but for only $170, performance wise it comes pretty close to a 660 or a 7850. Plus it has the capability to run dual SLI for future upgrades. That extra money could be spent on a better CPU or other places, and you won't give up a whole lot by going to the 650 Ti BOOST.
http://www.newegg.com/Product/Product.aspx?Item=N82E16814130909