Well I am seeing the 2GB Rx 460s go for as low as 140 euros here in Greece, and even if you need to spend 5-10 euros more you'd get a large performance boost for very little extra money.
It's the exact same reason I implore people not to buy stuff like the GT 730 or whatever, you spend your hundred bucks because you want to get your card as soon as possible and think "it's gonna be fine, they're exaggerating" and then you realize that it can't actually run half the games you want at playable framerates and you've pretty much just wasted a hundred bucks to save 10$.
Obviously, your situation is not anywhere near as drastic as that since the 360 can run virtually anything if you sacrifice resolution and settings, but still, due to the new GPU architecture, even if you have to pay a 10 euro premium you're getting an obscene amount of extra performance for that money, on top of which you get a much more power-efficient card (heck, the damn thing is a 75W card so you don't even need power connectors with most of them), which also translates to a much quieter card.
Having Gen2 PCIe isn't a problem. There's no card on the market that has any issue at PCIe x16 Gen2.