There´s really not too much difference:

 

http://www.pugetsystems.com/labs/articles/Impact-of-PCI-E-Speed-on-Gaming-Performance-518/#Conclusion

 

I was just going to write this... the difference is minimal

i'm on a 970m 3gb in a laptop and it's amazing.

I have just upgraded from a 560Ti 2gb to a 970 4gb. Not much increase in fps with fsx and dx10, totaly different with P3D 2.4, 50% maybe more..

Quiet and cool too

get a 4790K i7 from Malaysia or Vietnam batches. Then get a 970. I got a 4790k but im still in the process of squeezing the max out of it, planning on de-lidding it as soon as i get some supplies in. Then im going to install FSX and P3D. I'm running a GTX 770 SC 2GB which will be maxed out due to my 1440p resolution.

 

As for the brand, getting Zotac just because of lifetime warranty isn't the best imo. I would go for a G1 like everyone has suggested or a EVGA. You will be most likely upgrading again in 3 years anyhow.

 

Good luck

I have just upgraded from a 560Ti 2gb to a 970 4gb. Not much increase in fps with fsx and dx10, totaly different with P3D 2.4, 50% maybe more..

Quiet and cool too

 

This is kinda where I'm at - except my 570 only has 1.2 GB of vram....  I'm hoping for a boost in perf in P3D AND XP10 where on normal textures I'm getting less than 20 fps in rural areas.  

It's because you locked at 30 fps - the GPU will only use so much power in that case. With unlimited my gtx 570 is at max usage per nvidia inspector... And this is only 2x MSAA (in game settings)

i think ur on to something because my gtx 660 couldnt handle unlimited and started getting noisy cuz it was working so hard as soon as i locked it it stopped.