Damn, for that kind of cash you can get a killer frame made of lugged Columbus steel, chrome stays and fork, a real pedigree.

I've got nothing against aluminum frames but if you are willing to get a used frame I'd definitely spend the money on a lugged steel frame.

Better in terms of the ride characteristics. Good quality steel is as light as an aluminum frame unless you spend mega bucks for something like the Orbea Arin. The deadening of road vibrations is noticeable but it is not like you are riding some old beach cruiser.

If you aren't racing, then "lighter and stiffer" don't mean squat. The weight of a frame matters little once you have added bottom bracket, cranks, wheels, bars, stem, saddle, etc. Steel frames are plenty stiff.

You want that steel frame to weigh as much as the aluminum one? Pour out half of one of your water bottles.