thanks for your feedback guys!
yes, the i7-3930K I have also in mind, and I am looking also there for some nice setups.
Still I am not sure which CPU+GPU I should go for, regarding my needs.
But now that I can not go for a dual solution, maybe the i7 makes more sense over a singleXeon E5-1650 @ 3.20GHz?
point taken on the ECC, I am not that savyy in the finer details, so I have to rely on what the vendor is offering when I customize the workstation, what alternative can you recommend?
2 SSD: the idea behind is a very old-school one
one is for the OS + software only, the other for the WIP files. So if one goes belly up, I still have something saved
good, no good?
additional HDD: sure, I just wanted to keep it close to my initial budget and I can get this also later on. besides I have some external backup drives too.
I do not know about this detail, but I will need the workstaion to be pre-fab or custom built by a professional, as I dont have the skills/time to build it up completely by myself.
Thats also why it is quite difficult to find a PC that has all those ādesiredā parts in one system at a reasonable price.
If anybody knows a custom PC builder with a good price/performance ratio in the EU, please let me know 
If you guys had to choose, what would you go for, regarding the work to be performed as described in the initial post?
A: Xeon E5-1650, 3.20GHz + Quadro K4000
B: Xeon E5-1650, 3.20GHz + evga gtx 770
C: i7-3930K, 3.20GHz + Quadro K4000
D: i7-3930K, 3.20GHz + evga gtx 770