Ok, so I have a Asus GTX 275! My i7 920 is overclocked to 4,3 G's, so I am thinking of upgrading my videocard.

 

Mostly I see good fps in fsx, but when I use PMDG's NGX, Active Sky and some good scenery addons, it maxes in the 20's and drops to about 11-13 fps.

 

Do you think it would be wise to upgrade my graphics card? could that improve fps? need advice!

Your GPU is probably holding you back a little bit. Also, in very intensive areas, the older gen i7s are not nearly as powerful as one of the new SandyBridge systems.

I recommend at least GTX 560Ti, and GTX 580 will only give you improvement when you run high AA and SSGS levels, otherwise not.

 

Dispite the high clockspeed, your CPU is also bottlenecking you. I recommend upgrading to a Sandy Bridge system, you should see a pretty big improvement.

_{I upgraded a gtx 275 to a 560ti more than a year ago. For FSX, the upgrade did very little to help overall FPS but it did allow higher levels of AA/AF to be used. I also fly in Rise of Flight, and for that sim the upgrade was most worthwhile. Games such as Skyrim will also benefit greatly with that upgrade.}

I had pretty poor FPS with my new IB build with FPS somewhere in the teens and 20's IIRC, even at stock using an 8800 GTS 512, bumping up to a GTX 680 made an immense difference. I never intended to use the 8800 btw, just a place holder until I could get my hands on a 680. A GPU upgrade would likely help in your case though with your system having less CPU horsepower I can't say by how much. Any chance you have a friend with a faster card that would let you borrow it for a day to test?