I was thinking of getting the hd 7970 oc 3 gig:
http://www.pccasegear.com/index.php?main_page=product_info&products_id=19269
but then i saw the gtx 670 oc 4 gig:
http://www.pccasegear.com/index.php?main_page=product_info&products_id=21726
is it worth getting the 670, or should i stay with the 7970, alternatively should i get an intirely diffrent graphics card?
Go with the 7970.
There is only one, maybe two, situations where is see my 7970
(its in crossfire but as you should know that doesnt double the vram)
hit the 3 GB limit. its skyrim with all the texture addons. other than that, maybe crysis3. And i use eyefinity (5040x1050).
maybe 3 GB becomes a need in the future. It might be good to have it already. Not saying that!
But for the present... I feel like 3GB has 1 GB too much to actually make a diffrence at all....
So about your question; 4 gig is overkill. 3GB is ample. Even for the future.
It's not just about how much memory, bandwidth matters, too.
A stock 7970 has 50% more memory bandwidth than a 670/680. That means where the 670/680 can be slowed down by hitting a bandwidth bottleneck, a 7970 has more than it could ever realistically use.
Adding more memory has next-to-no effect if the GPU can't effectively use it all anyway. A 4gb 670 is kind of a trap for people who kind of know what they're shopping for. If you know you'll need more than 2 gigs, it looks like the perfect solution; it's exactly the same thing, but with twice the memory. But no, the amount of memory a 670 can effectively use under most circumstances would be less than 4 gigs, that's why Nvidia didn't put more than 2 gigs on there stock. Stuff will technically fit in memory, and technically be (somewhat) faster than not having the extra 2 gigs of memory, but it just moves the bottleneck around a bit. Not worth all that money over a regular 670, if you ask me. Same situation with the 4 gig 680s.
If you're looking at high memory usage for a GPU, you should probably be looking at a 7970.