Optiplex 7010 MT ... doing a 2016 video card and power supply upgrade and memory

I recently purchased a refurbished Optiplex 7010 MT. Core i7 3.40GHz 4GB RAM, 250GB HDD, DVDRW, 7P

Minor side issue: I have already ordered the memory to upgrade it to 32GB RAM based on the advice of the store that sold it to me and Crucial.  Unfortunately, if I read the dell-optiplex-7010-manual-en.pdf right.  It can take 8gb RAM but only two of them for a total of 16gb.   Is it possible to utilize all four 8gb DIMM?   If not, the importance of the speed of the graphics has become even more important.

I need to upgrade the power supply and video card to run Adobe software -- Photoshop, etc. Based on prior experience, I need the fastest possible graphics option.    I'm thrifty but not stingy ... if I can get a racehorse for a bit more then I will.

The video card that I'm thinking about buying is the GEForce GT 640 recommended by Dell. Is there a specific version since the specifications also say "(OHGA3/M209N)"? I would prefer to be able to use a card with more memory but still PCIe 3.0 which appears to be much faster than the PCIe 2.0. If there is a better card out there, please let me know.

The power supply is standard. Since this is April 2016, the Dell recommended Corsair 650TX appears to be hard to get at best, Is there another power supply that would work?

Thank you for your help. Much appreciated!

*** Reposted from being reply to older question.  Wasn't sure if that thread had been closed and no longer monitored.  ***