If you plan on only getting 16 Gb in the future, then the Windows Home Premium would be enough. Unless, ofcourse, there are Windows 7 Pro features that you need in your work.
A full tower is too big in my opinion. A nice mid tower will house all those with ease and still get great cooling. Something like the Corsair 500R or the Cooler Master Storm Enforcer.
Check these PSU's too and see which ones are cheaper: Corsair TX750 or XFX Core Edition 750W. They're also good and reliable.
I would also consider the Crucial M4. Its slightly cheaper than the OCZ Vertex 4.