Just got back from Guitar Center, and ended up buying the Fender Rumble 100.
I checked out the Rumble along with the GK MB112 and the Markbass Mini CMD 121P. I also checked out the other small combos in stock from Ampeg, Acoustic, etc.
I went in the store thinking that I'd buy the MB112, or that I'd be impressed enough with it that I'd order an MB110 online since they didn't have it in stock but it would be smaller and lighter.
The GK sounded good, but if I pushed it a bit it started to have that boxy tone that I get from my Eden EC10. Not a good sign since that was a 12 and had way more power. Could just be the voicing of those amps though, because I can even hear some of that boxy sound on the demo videos that Norm Stockton did for them on YouTube for both the MB112 and MB110.
In terms of portability, it was light but the depth of the amp would make walking a long distance with it in hand an it awkward.
The Markbass would have had to blow me away in terms of portability and tone to get it since it was over twice as expensive as the Fender and exactly twice as expensive as the GK. But it was still in my budget, and I used an LMII for YEARS and loved it so I wanted to check it out. It sounded good, but not great. Definitely not spend twice as much great. Form factor was similar in depth to the GK and weight at 30 lbs.
I wasn't happy with the tone of all the other amps I checked out - Ampeg, Acoustic, a used Hartke, etc. So I didn't even try picking those up to feel for weight.
That brings me to the Fender. Wow - blew me away with the tone when flat and the versatility if I wanted to tweak it. I typically never use "bright" or "vintage" switches - for controls like that I want a knob so I can control the amount vs a switch. But at least in the store those switches were VERY usable. Also I'll never use the overdrive on my jazz gigs but MAN it sounds good on that amp. I need to research to see if they make that in any kind of pedal because it sounded so good. I tried pushing the volume on it way past what I'll need for a cocktail hour and never heard the boxy tone you can get from some small combos.
In terms of portability it was by far the lightest, and had a good form factor without too much depth so I think it will be easy to schlep in and out of a gig in one hand.
I didn't end up bringing my MTD to the store to test, so I'll do that at home. I'll be able to get it out on a gig next week to be absolutely sure that it will work.
I was also impressed with GC - I hadn't been in years, so wasn't sure what to expect. When I told them what I wanted to buy they went in the back and got me a new one in a box. I figured they'd give me the floor model, but the rep said they keep a ton of the Rumbles in stock because they sell like hotcakes.
Thanks to everyone for the suggestions - I hadn't even heard of this amp before making this post. That's what TB is all about!