I have heard both speakers many times (though never in the same system - perhaps that disqualifies me). Both are excellent. They have different flavors. I agree with Triode in that when they are well set up, they don't have 'poorly integrated' bass, but that it takes more work to set them up than it would the K2s. I don't think either will be regarded as particularly good financial investments but either will provide a great amount of satisfaction. For some reason, and I am not sure why, I think the K2 does all things at a very high level, and the AGs do most things at a slightly lower level of perfection but some things even better than the K2s (Inman29's 'illusion'). I also like bass a bit further down than the JBLs can go, but that's me. The K2s' bass sounds really, really great.
About the keeping the BAT pre/power, my personal inclination is to say that the AGs really shine with a SET amp. The K2s need more juice than the AGs and your BAT amp is probably enough for the K2s (though if I were starting from scratch, I'd tend to want a bit more than 55W.
About the keeping the BAT pre/power, my personal inclination is to say that the AGs really shine with a SET amp. The K2s need more juice than the AGs and your BAT amp is probably enough for the K2s (though if I were starting from scratch, I'd tend to want a bit more than 55W.