The major differences was that I put an AMD XP 1700 processor instead of P4-2.0 offered at Dell. But I paid $89 in the retail box for the processor, and $79 for a single CPU motherboard w/onboard ethernet and 4 USB ports and 6 PCI slots on board. I also got a 60 GB HD for $89. The Standard Dell system comes with 128 MB of DDR ram, and upgrading it to 512 was $150 extra. I paid $109 for 512, and didn't have any "trade value" on the 128. $40 here, $20 there, it adds up fast.
These are the way Dell gets you -- by placing an inherent value on the base system of about $600, but then by the time you "upgrade" it they nab another $800 out of you. It's fine for those who want 1 machine and no worries or hassles, but I am constantly getting new machines (3-4 every year it seems!) and that adds up to a lot of money.
I get exactly what I want, nothing more nothing less. Of course, something could go wrong, as in the case of my case. But that could also be true of Dell. Just a random chance that I would get a defective case. The new case I got is way cooler, and cooler than any case I've ever seen. Cost me a bit more than the other one, but it's all aluminum with an internal glow light and a plexiglass window... the machine glows (plus the light enables you to see what you are doing inside the machine).