Currently my main amp is a Fender Rumble 500 2x10 combo. The power is more than adequate for anything I do, and the EQ is flexible enough that it works in a variety of environments and styles. I play upright and slab, classic rock, blues, a few jazz standards, and a lot of backup of acoustic acts. I use a Tonebone PK-Pre(amp) for the upright, and can do DI from either the preamp or the Rumble. A while ago I played through an older G-K 400RB 1x15" combo, and loved the sound, particularly with my Lakland. It isn't as dramatic with a passive bass, but it's hot with the Barts. I'm also told G-Ks are really good for upright, though I have not tried one with mine. I'm thinking of picking up a G-K, but I'm not sure which. I've read there are significant differences in sound between the RB and MB series, that the 400 and 800 are significantly different, the 1001 is a whole 'nother beast entirely, and that the power section (and maybe cabs/drivers) are critical to the sound as well. Then there's the Plex preamp, which costs as much as a used head. I don't think I need the full 500w (350w with internal) from the Rumble, as even with the last loud drummer I played with I never cranked it, and frankly, my days of playing at high volume are over (I'm 57 and have bad tinnitus). I like the idea of the lightweight G-K amps, and indeed, don't want anything that weighs over 35lbs or so. I'm thinking that I'll eventually end up with a Greenboy cab like a f112, though I could go cheaper, and even happen to know of an MB212 available locally. Can anyone help me out and give me some direction with which G-K to look at? Or is the correct answer, "Any/all of them!"?