I'm thinking of upgrading my gtx460 and I don't know whether or not to get a 670 or 680, could some one please clarify how substantial the difference is between the two.

Also, how much more power does the 670/680 require compared to my 460? Might need to get a new power supply.

If you listen to the tested podcast, last week they talked about this for quite awhile, Norm seemed pretty convinced that there is no real need for a 680 over a 670 other than getting an extra year out of it before your next upgrade.

I wouldn't think the 670 would draw any more power than your 460, one of the big improvements has been power consumption.

I've been looking at getting rid of my 2 gig hex output 5870 and was in the same predicament.

Asus has an overclocked 670 with a huge PCB that is not only clocked higher than a reference 680, but just as fast, if not faster. For a hundred bucks less. I think it measures out at 10" length; the stock 670 is ~9". I've always been a big believer in buying close to top tier, but never top tier. By the time the 670 feels slow, the 680 is going to feel slow, too. I won't notice a difference between 160fps and 180fps and by the time the cards are near their end of life, 26fps feels just as sluggish as 33fps. I'd rather have the hundred bucks put toward something like an SSD or paying off bills.

http://www.hwcompare.com/12531/geforce-gtx-460-vs-geforce-gtx-670/

The 670 uses a bit more power, nothing drastic, though.

@Zelyre: Alright cool, I did some research and a 680 is only 4.5% better than the 670 and it's 100 dollars more.

Also, do you know if the 670 has the same physics capabilities as seen in this http://www.youtube.com/watch?v=jptcT8R-yuc tech demo.

I went 670 FTW and I have no regrets.

It's a 670 built on a 680 PCB...I'm pretty sure. So it's like you get both...

GTX 680 is 5-10% faster for $100 more; not really worth it.  
 
The TDP of a GTX 460 is 150-160W, and 170W for a GTX 670. You won't need a new power supply.