Perfect for the price man. Nvidia GPUs are a bit overpriced at the moment for what they deliver. The only suggestion I would have is save up another 100$ and get a r9 280, but don't get a 270x, which is just a stupid product. The 270x is the exact same as a 270, it just has a very slight overclock. When both cards are overclocked to the limit, there isn't a single damn difference between the two. So the next step up would be a r9 280, such as this if you like the MSI one specifically:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814127789&cm_re=r9_280-_-14-127-789-_-Product or this is you don't really care and want to save money:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814121867&cm_re=r9_280-_-14-121-867-_-Product both are amazing cards. I have a MSI twinfrozr cooler myself on my GTX 680 Lightning, very awesome cooler, though the ASUS DCUII is just as good.
As for PCI, even the highest end GPUs, such as a 295x2 running on PCIe 2.0 x16 would only lose about 5% performance at most. A 780 would probably run on PCIe 2.0 x8 (3.0 x4) just fine.