Agreed. I built my own system a few months ago, keeping only the old HD and monitor, and it destroys any store-bought box I've ever owned - not to mention being cheaper.
If I had a mind to, I could probably overclock this bad boy up to 3GHz. But I'm too conservative. ;-)
Add to that, I'm on DSL with a connection that typically runs 1.5Mb/sec and I'm a happy camper.
I could also tell you about my PowerMac Dual 1 GHz box with 1.75GB of PC2700 DDR RAM, and nearly a half-terrabyte of hard drive space.
The coolest thing about my Mac setup is the Granite Digital FireVue IDE/Firewire Hot Swap drive enclosure. When the removable drive tray is inserted and the lock is set with power on, there is a very cool blue neon light that runs across the front of the drive tray. Sexy, sexy, sexy.