E3-1230/40/45 vs i7-3770

Hi all, I currently have a Dell 1557 with i7-720QM which has been great over the last few years, but recently I have started dabbling with 3D modelling, nothing too heavy just for fun and also bought crysis 1, both activities make my laptop struggle and so I have started thinking about building a desktop computer, I have looked at the cost/power of various processors and have worked out that the E3-1230/E3-1240/E3-1245/I7-2600/I7-2700/I7-3770 all come out about the same when you work out the power per £1 in cost, If i was to go for an I7 i would go with the 3770 but with regard to the xeons my questions are:

A) Would I be able to get a duel socket motherboard but just run one Xeon processor until I feel the need to add a second?

B) Considering I will be adding a graphics card with CUDA cores to help the 3D & games stuff out is there any reason to go for the I7 over the Xeon or vice versa?