I haven't heard the Theos or the Montis but since no one else is jumping in here's my 2 cents. Many ML owners feel that the larger panel of the Montis is an audible improvement over the smaller panel of the Theos.
Next, the new hybrids (especially those with the powered woofer) are supposed to be ML's best integration of panel and woofer cone yet. The Montis should have plenty of bass, unless you're a bass head, so reducing the number of crossovers and trusting that ML can do the transition from woofer to panel better than you can makes the Montis sound pretty enticing.
I'm a believer in the theory that in the real world (sub $100,000) speakers can offer the biggest upgrade bang for the buck. You could take all this out of the realm of theory and haul your speakers down to the dealer's shop and compare them to the Montis.
Next, the new hybrids (especially those with the powered woofer) are supposed to be ML's best integration of panel and woofer cone yet. The Montis should have plenty of bass, unless you're a bass head, so reducing the number of crossovers and trusting that ML can do the transition from woofer to panel better than you can makes the Montis sound pretty enticing.
I'm a believer in the theory that in the real world (sub $100,000) speakers can offer the biggest upgrade bang for the buck. You could take all this out of the realm of theory and haul your speakers down to the dealer's shop and compare them to the Montis.