I can get a GTX 590 which is more powerful then a GTX 670 for around $400, should I do it or just do the buy GTX 670 for now thing and SLI 670's later down the road. The 590 won't probably need an upgrade for awhile.
Go for the 670, much lower power, and more importantly, quieter. You can SLI later when it's necessary and still be at lower power and noise.
I don't really care about noise dude, I have an air conditioner in my room blazing and bunch of case fans and I wear big padded headphones so I don't hear much outside of it anyway. Power is really of no concern also, since both cards would be fine with my power supply.
So if I can get a brand new ASUS GTX 590 for around $400 should I get it or nah? Like I said, noise is of no concern and power is good with my power supply. It outperforms even a GTX 680 and for less money. Would probably be good until next year I'd imagine then I could sell and upgrade to a new GK110.