First off, that's a cool girlfriend you have man
Second, I'm still baffled on how Dell can sell XPS systems with i7's and only put a 6450 in them? Not your fault, I'm just pointing out something that I've always hated (and the fact that they rip people off if you upgrade the GPU when configuring it)
With that said, a 570 is a great card. Don't worry about the 600 series, your card will work fine for at least until the 700 series, maybe even 800.