i'd prefer a match of i7-2600 with a Nvidia GTX470 or 480 but dell do not offer that choices at all... and I am not sure if I can replace the card by myself afterwards as am not sure the PSU is able to support... hence, appreciate advice from you all. thanks!
Just from the specs you listed and if you have to buy right now
I would go with number 3 due to larger more stable ram support plus Quadro is designed for workstation graphics rendering (better driver support) also if the board is a dual socket design where you could add another W3530 later that futureproof you.
I would pick the I7-2600 but with the cougar chipset problem I would be
worried about problems later.
If you can hold off a couple of months then go with the I7-2600 build
when the motherboard problems are worked out.
Also if this is for professional purposes with money on the line then
I would look into some of the custom builders like Cyberpower or Boxx
for example.
Try a Precision, Graphix options on these ones are good for rendering (including what you aim to do).
I'd go with an i7, remember it's got 4/8 threads.
BTW, go with a 2 memory sticks config, in case it crashes, & RAM is the faulty component, it'll be easier to find out. Having only one will make you scratch your head & hesitate between Motherboard or RAM.