Yes, the Schroeder Mini12 speakers--I have one of the original angled and ported Mini 12+ cabinets and a front-facing, sealed mini12+Light--are very efficient and can get really loud. I have switched over to an AI Focus amp as my main gigging amp, and it produces more than enough power for any possible gigging situation, on both upright and bass guitar, with any cabinet that I've tried, including an Acme B-1. However, I still own a New Yorker, which was AI's first light weight combo amp and it has a ClarusSL amp in it that produces a maximum of 350 watts at 2 ohms and 250 watts at 4 ohms.
Wilbyman, who I think started this thread, owns a ClarusSL amp and he asked me about volume using the Mini12+ with that amp. Yesterday, I disconnected the built-in SL amp from the Contra EX speaker and hooked it up to my Mini12+light, and spent time playing my upright through this. This combination gets way louder than just the built-in EX speaker and I think it sounds wonderful with upright. The sealed Mini12+L has a bigger low end than the ContraEX speaker although it isn't quite as hi fi, perhaps because the EX is a 3-way and not a 2-way speaker like the Schroeder. The sealed Mini12+ is very smooth sounding and doesn't have the "edge" that is characteristic of the Schroeder speakers I've heard--this edge is what makes them so fantastic at cutting through a mix when playing with others. OTOH, the mini12+L doesn't sound flabby or boomy like some bass guitar cabinets do that have scooped mid's (I"m thinking of the single 12 Aguilar), which sound makes them not so good for upright. Anyhow, the ClarusSl driving the sealed Schroeder was able to get loud enough that feedback finally became a problem, i.e., loud enough for any situation that I face when working.
I know I'm on the Bass Guitar forum, but I'm sorry that I didn't have the time to put this combination through its paces with my bass guitar. However, I'm sure it will sound equally good with bass guitar. It is my intention on doubling gigs or any gig where I'm concerned about volume (e.g., an outdoor gig with a loud band) to bring both my Mini12's and drive this combined 2 ohm load with my Focus Series III that produces 1000 watts at 2 ohms. If I had to pick another speaker that the sealed Schroeder sounds like, I'd say it was the Acme B-1 but WAY more efficieint. I love the sound of the B-1 but found that it took a big amp like the Focus or a Walter Woods Ultra to get it loud enough for loud gigs. I sold my Bergantino Ht-112 some time ago so couldn't do a real time comparison but I like the sound of the sealed Mni12+L way more than I did the HT-112 for upright. Hope this is helpful.