GPU Advice

Hi guys. I build my first PC a couple of weeks ago, but couldn't afford a GPU at the time.
My specs are:
Intel Core i5-4670K Box, LGA1150
8GB-Kit Corsair Vengeance PC3-14900U CL9
ASUS Z87-PLUS (C2)
Fractal Design Integra R2 650W
Zalman Z3-Plus Midi-Tower
1 TB Seagate Barracuda 7200rpm HDD
Win 7 x64

The board has 2 PCIe 3 slots
The PSU has 2x 6+2 connectors
My budget is around €200.00

The main reason why I'm dithering over this, instead of just going with a
R9 270 or a GTX 660, is that I'm unlikely to upgrade again in the next 5 or 6 years, and was wondering would these still pass the recommended specs (as opposed to minimum) for games at that time. At the moment, I play Skyrim exclusively (on xbox), but that doesn't mean that won't change. If Bethesda comes out with a new TES game, I'd certainly be interested.

My main interest at the moment is to mod Skyrim on my PC. (And do some virtualization; I'll throw in some more RAM for that)

I would appreciate any advice.