X51 PC's With Different Specs. I3 2120 , I5 2320 , I7 3770

Hi guys! 

I am planning to do a survey of how many of you guys have the X51and which one did you chose ? I know there are 4 with different specs : 

The first one with Intel® Core™ i3-2120 3.3GHz (3MB Cache) with Hyper-Threading Technology, 4 GB of ram & 1GB GDDR5 NVIDIA® GeForce® GT 545.

The second one with intel® Core™ i5-2320 3.0GHz (6MB Cache) with Turbo Boost Technology 2.0, 6 GB of ram & 1GB GDDR5 NVIDIA® GeForce® GTX 555.

The third one with 3rd Gen Intel® Core™ i7-3770 (3.4GHz, 8MB Cache, w/ Hyper-Threading and Turbo Boost 2.0), 8GB of ram & 1GB GDDR5 NVIDIA® GeForce® GTX 555.

The fourth one with  3rd Gen Intel® Core™ i7-3770 (3.4GHz, 8MB Cache, w/ Hyper-Threading and Turbo Boost 2.0), 16GB of ram & 1GB GDDR5 NVIDIA® GeForce® GTX 555.

I am planning to get the second one with i5 2320 3.0 GHz, 6GB ram and GTX 555. 

I was wondering how future proof will this PC be ? i know these PC will be up-gradable but with limited power supply it will be hard in the future. But there are good GPU at the moment such as AMD 7850, AMD 7870 or GTX 670 which we can upgrade to. For now this are safe GPU upgrades. I am not sure how long these will last. I am hoping these specs should at-least last for couple of years. In  couple of years there will be new GPU and newer games with lots of requirements. 

What do you guys think of Intel® Core™ i3-2120 3.3GHz ? will it be a good processor for gaming & other stuff ? reason why i am asking is if its good then why not buy that and and just upgrade the GPU. 

So hoping to interact with you guys on the specs and your opinions about this X51. 

Thanks for your attention!