So you say you want the loudest small cab, but then you say your previous (combo) cab was too loud. That doesn't really make sense.
Is there any reason why you need something smaller than a 1x12? If not I would probably go with the bass array 12. I just got a pair of the Genz Benz STL 112s, and they're not exactly back breakers. But I also wouldn't want to gig with less than 2 of them, but if you play music where the bass is a background instrument, or play really small places, 1 might do ok. I tend to play dynamic music where bass is prominent, and I play 5 or 6 strings usually, with effects, so I need to have a decent amount of headroom. Heck, I took those cabs to an audition the other day which was on the guy's back porch, and the cabs were a foot from the wall, and I still felt like I could have pushed more volume on the amp to play a bit lighter. Although I was also too close to the drums (with earplugs).
It seems like either you want a really small cab, in which case you set aside volume, or you want a pretty loud cab in which case you set aside size. Personally I would never go smaller than a 1x12, but if you're needs are modest maybe you could get away with a really good 1x10.