My 5-year old Dell doesn't cut it anymore!

Dell's aren't that bad for the price, but they're terribly unfriendly to the person trying to upgrade their computer. All proprietary computers do this, but Dell is pretty notorious for it. (I've seen Dell motherboards with only PCI slots, no AGP, no PCI-E)

Are you building your own or are you buying a brand name one?

You have a LOT more possibilities (infinite) if you build one yourself. But buying a pre-made saves you the trouble of putting it all together.

Either way, what's your budget? From a more numerical perspective, since your current budget is pretty subjective.

Finally, do you plan on gaming any? Video Editing? Server Running? etc.

Jam it back in, in the dark.