More power for my Duos?

I also would recommend the Audiopax...while I did not specifically use the Avantgarde I was using a 103 db horn and had both the Audiopax 88 mono's and a pair of wavelentgh custom 45's which were designed to be superior to the venus. I also had a pair of custom Fi 2a3's as well as a pair of Komura 845's. The Audiopax was the overall favorite but all were excellent...the Fi and Komura otstanding but offering a bit too much noise for my rather low listening levels.
The gent I bought the Audiopax from had the trio's and was upgrading to the Lamm ML2.1's (the SET's)...after a month I'm not sure he was convinced he had made the right choice.

One of my customers is using Kronzillas with his Duos and likes them...

I am using the Audiopax 88s with the Duos and they are very musical and plenty powerful to play at live levels. They have a very quick warmup 10 minutes to sound good. The timbre lock controls are one more way to dial in your sound are quite useful.

The Duos are very picky speakers about everything in the system being just right especially the positioning of the speakers and the crossover setting.

I am convinced that Luke above did not exhaust his efforts in making his Duos sound good, otherwise they would sound great. The Duos having a powered subwoofer and crossover control are anything but lean sounding. Even though there are only 2 controls there is a lot of possiblity for integrating the woofers to the mid horn and if done right they won't sound lean.

You ask about Art Audio's Jota. I believe that for use with Duos, Art Audio recommends their fine PX-25 amp, either the stereo or the monoblock versions. Your specific requirments would determine whether the monos or stereo version would work best for you. I talked to Art Audio a while back and they use Duos in-house, so for sure they would be a great resource for you if you contact them.

I have a pair of Duos at home (paired with Tron Meteor and Quad IIs). The Duos are so efficient, you don't need more than 4-5 watts. However, whatever you use must be quiet and good as the Duos are very revealing. I have heard the Duos with the Tron PX25s (5 watts) - sublime. I agree with Ejlif - play around with positioning and subwoofer setup. that's crucial. Mine were set up at home by Graham Tricker from GT Audio (UK distributor for Avantgarde and manufacturer of Tron amplifiers) - that's part of his service in the sale price.
In my room (35 x 20 feet - 12 foot ceilings), the subwoofer crossover freq is set at 170 and the volume at the 12.30 clock position.