i have two 560 TI 2GB editions, and i play with over 120 mods @60FPS with Vsync on. with a single 670 you will be fine... the only thing i WOULD warn you about: Skyrim has been know to work better with a good CPU, i dont know what you have, but it has been shown to play better with faster CPUs
560 Ti master race! But yeah, it seems that in Skyrim, a good CPU is very beneficial. I found myself getting 5-10 FPS more with the overclock I did on my CPU.