Hi-
The 933 MHz processor is like night and day as compared to the 733 OR the dual 800.
Definitely get a 933, especially if the price is right. Even better, is a dual 1.0 GHz...
BEWARE of overclocked 733 cards claiming to be 933, but having no L3 cache.
Whether you think that you do or not, you
need a better graphics card to really round out performance.
The Radeon 9800 Pro is fine, but you can use a flashed radeon 9800 XT or, even better, a flashed Geforce 6800 GT in the QS.
Of all the cards that I have used, the Geforce 6800 GT stands out as the best performance value available.
Here are a few test scores in a QS, starting with Page 1 of 7:
http://www.jcsenterprises.com/Japamacs_Page/Page%201%3A%20OpenGL%20.html
Get an idea of processor performance:
http://www.jcsenterprises.com/JapamacsPage/SystemBenchmarks.html