Comment Mac Pro? (Score 1) 2
I can't comment much on whether this is a good route to go, other than that I am seriously looking at that route for my next upgrade. I am going to take your questions in reverse order.
1) Win-X cannot use more than 4 Gb RAM period, and effectively is limited to 3.5. Giving it more is a waste. Given your applications, give it this max. Keep in mind under virtualization, any memory given to Windows is not available for OS-X, so you should look at a minimum of 6 Gb of RAM.
2) Dual boot? Only worth while if you are not going to use virtualization. Of possible utility while you are getting the virtualization running bug free, but why not just use your old computer until that is done. I see it as another area to run into problems.
3) Virtualization. You indicate you have had problems with Parallels, have you looked at Sun's Virtual Box? It is Open Source under the GPL license, and is free. It can't hurt to give it a try, and being open source, with a major vendor behind it, I would imagine that any issues are likely to be resolved fairly quickly. (http://www.virtualbox.org/)
Just my two cents.