If you know you are going to be doing some obsessive part upgrading, then plan to put in as many gears as you can into that rear hub. I'd recommend a Nexus 7 or 8 speed, if your chopper of choice doesn't already have one. If you are feeling wealthy and luxurious, you can put in a Rohloff 14 speed internal speedhub.

If you've got the gears, you can push the weight, the worst is a heavy chopper with poor gearing. But with good gearing it can be heavy or light, and still be a pleasure to ride.

Also, keep in mind that wider wheels/tires means a lot of rotating mass, and rotating weight is a lot more important than non-rotating weight, as far as the ride is concerned. Wider tires = slower accellerations, regardless of the rest of the frame weight, so take that into account as you shop.

Enjoy your chopper!

peace,
sam