That should give me an awesome boost but am I overlooking my CPU and mobo ? I'm not really wanting to spend much more and if I do I might as well build a whole new PC. The only game I play often is Battlefield 3, otherwise it's just a video watching / browsing machine through the home theater.
The first gen i5's are starting to get a little dated, but they're still pretty capable. You shouldn't need 16GB of RAM for anything you listed, and if you aren't running 64-bit Windows, anything more than 4GB can't be addressed (wasted space). Those upgrades should give you another year or 2 based on the slowing speed of desktop power and PC game progress.
GSkill Ripjaws or Corsair Vengance are both very high quality and can be trusted. 1.5v DDR3 1600 cas 9 is the sweet spot for price/performance. 8GB is fine for almost anyone unless you do CAD or photo / video processing and work with huge files regularly.
The i5 750 is still a great processor but you might want to think about a good aftermarket cooler to overclock it. It would help you get the most out of your new GPU. Something like the Colermaster Hyper 212 Evo is a good low cost option that should get you a good extra gigahertz or more. Much cheaper than a new board and CPU and with the other upgrades would really unleash the potential of your hardware.
Edit: If you do go wih an aftermarket cooler get either any GSkill Ripjaws or if you get the Corsair make sure it's the low profile Vengance. The regular Vengance has high heat spreaders that can get in the way of a big air cooler. Same RAM just different heatsinks and DDR3 does not really even need those heat spreaders as it runs cool anyway.
I've got the same dilemma. Have the exact same CPU (i5-750).
What I did to my setup was to upgrade my ram to 8gb (2x4GB G.Skill RipjawsX 1600MHz), get myself a samsung 830 ssd (120 gb), Get a CPU cooler (Hyper212+ EVO) , GPU (GTX 560), and Overlock to 3.2Ghz (pretty conservative OC due to my bad mobo)
It runs pretty well. I would think that upgrading to the newer processors (sandy/ivy) would not be worth the money considering the performance-price ratio of the upgrade itself. Maybe when haswell is released, that may be the time to go for the upgrade.
I'm pretty good with all technology but overclocking is something that I haven't ever played with. I'm hoping this upgrade will be enough that I won't need to overclock or mess with a serious cooler. The again it might be time to learn
A conservative OC would be best. I managed to OC mine from 2.66 to a stable 3.2 without changing the voltages. Go ahead and OC your i5, you won't really get the most out of your CPU / Money without overclocking. They've built those chips and boards to handle A LOT more than their default clock speed. Some even go as far as 4.4 GHz on the i5-750.
Then again, I don't really see that specific CPU being a bottleneck. Although it is dated, it can still hold its own with ease. You will definitely benefit from the OC if you run CPU-intensive applications or games (such as video editing, games like sleeping dogs or gta, file compressing etc.) Other than that, a decent ram for multitasking, and a decent gpu for gaming and you're pretty much set for another year. I would know since I have the same setup.