My vote is for a PODxt live with all the model packs added. Or, you could just opt for a lower wattage amp.

I use a 5150 2x12 combo, and it is amazingly loud. But, since it gets most of it's gain and tone from the preamp, it still sounds good at more manageable volumes. I've also got a Traynor YCV50 1x12 combo, but it sounds a bit too thin when played at very low volumes. You don't have to crank it to insane levels to get it cookin' though.

However, I can get similar tones to either of those amp, plus a butt load more, with my PODxt, and a Behringer DEQ2496 when I need a little help reaching that extra 5% of the tone I'm missing. The best thing about it is, I can get those tones at any volume I want.

If you go the PODxt (or any modeler for that mater) route for live stuff, I would definitely suggest a good monitor system. Also, be prepared not to be able to "feel" what you're playing. In the end, you're making a sacrifice, but the audience won't know the slightest difference, and the soundman and your bandmates will love you for it.