Alliedassault - Forte needs computer help...

I dont trust myself building a computer on my own (heavy handed). My dad said he would pay for it, and write it off as a company expense, as long as I work for 6 months for him.

I will be mapping, and gaming (ofcourse) with the computer. Mapping takes a hell of a lot of processing power, and a lot of memory.

my choices for processors is between the AMD 3800, and 4200. Would going up to the 4200 be that much of a performance boost? Or would I be better off sticking with the 3800?

When it comes to graphics cards, 7800GTX or X1900?

I have basically everything else covered. just need to know about the processor, and graphics card.