Hey Mad Dog,
You can always install memory later. Those big companies can some times be expensive for memory upgrades unless the are having one of those free upgrade offers.
www.crucial.com is an excellent website for memory. They are part of Micron. You just tell it what machine you have and it gives you the choices.
Since you are using CAD programs, a 19 inch monitor or bigger would be sweet.
Some times circuit city will have floor models of monitors or systems on sale.
www.salescircular.com is a good site to watch. Some times you can find some excellent deals.
Good luck.