I'm looking at building a new machine for doing .NET development on. I'll likely have everything installed on this one box - Win7, IIS, SQL, and I'm not sure what is the most important thing to squeeze into the budget.
For example, would going from 4GB of RAM to 6, or running RAID 0 on the OS drive give me more of a boost?
Also, it doesn't seem to me that a quad core would give me much benefit over a dual core.
Lastly, I'm wondering if, for this type of work, there is a difference in the performance of say an i7 vs an equivalent AMD.
You are going to be multi tasking. Get a big CPU. AMD does not hold a candle to anything i7, except maybe their hex core. If you are compiling large programs, running intense sql or the like, then you will want as much horsepower as possible. Unless you are building games, graphics will not be a priority.
If you want a throw away machine to get started because you are broke, then by all means select a dual core to save a few dollars today and buy a quad core after your first gig.