I'm looking at the lowest priced Compaq, SR1000Z with AMD Sempron, at their customize site starting at $499.99, click http://tinyurl.com/3vxs5
Ok, at that Compaq customize site we change the processor from AMD Sempron to AMD Athlon XP3200 (2.2 GHz) which adds $30.
Then we change the hard drive from 80GB to 160GB which adds $50. Everything else is similar to what you show. (However, I meself would want the Video card upgrade from the Integrated graphics.)
Total price $579.99, but notice it does not include a monitor, nor did you mention a monitor in your setup.
So, to customize a Dell, you go through about the same procedures. It should be noted that Dell changes their setup on what they give away just about every week, so it is usually best to watch for some time to get the right free stuff you want with the best overall prices that they shift around.
The lowest priced Dell Dimension 3000 is $499 at this customized site click http://tinyurl.com/55cb2
It is a Pent4, 2.8GHz. Configuring the exact same components as the Compaq (including the 1yr warranty), but only has Intel Integrated Extreme graphics2, it comes to $747. Also note it includes a "Free" 15 inch Analog Flat Panel (LCD) monitor. If you elect to not take the monitor they only subtract $50....(Gee they should take more than that off), but in weeks to come they will switch around what is free and the prices.
So, Compaq $580 plus their 15 inch LCD Flat Panel Monitor $240 = $820. However if you get the Compaq without a monitor, you can purchase a 17" conventional CRT monitor elsewhere for $100 or less.