Bang for the buck wise I highly recommend the Peavey PR12. I've never owned a pair, but I do have first hand experience of them in a real live situation.

Like these.

http://cgi.ebay.com/Peavey-00583900-PR12...=item5ad677803e

Pros : 1. At ~25 lb they pass my liftability test. (barely )
2. They sound good at LOWER volumes as well as higher.
(subjective: ymmv)

Cons: 1. Its always a bigger hassle to set up a pa arrangement
than an all in one solution.

2. Using them as a straight ahead instrument amp can be
problematic unless you have some really good signal
shaping and compression devices for you instrument,
used as a preamp in the signal chain.

Hope this helps and best of luck in your search. Be sure to audition what ever you decide on first.

Later,
Jim