I think i can help you with this our setups are quite similar. Here are my system specs:
AMD Phenom II X6 1055T
Asus HD 7750 820Mhz
Corsair Vengeance 2X4GB 1600Mhz
Acer X193w 1440x900 resolution
My computer runs all my games fine at medium to high settings (BF3, Skyrim, Simcity, Planetside 2 etc) But one day i wanted to record some gameplay and upload it to youtube just to show other people how surprisingly good the HD 7750 was but once i started recording with fraps skyrim started lagging hard and became unplayable even when i slightly lowered the settings. I tried a different recording program but that didn't change anything.
So in my opinion at least the HD 7750 with likely run all of your games (even most modern games) at a reasonable setting with playable FPS but if you are planning on recording i would personally buy the HD 7850 2GB because it's a smarter investment and is just overall a more powerful and capable card.
Edit: I'm not entirely sure recording was laggy because of my video card, i don't have much experience with recording video.It was probably because i have only one hard drive and the footage was saving to that as i was recording.