Martin Logan Vantage vs. Summit / Summit X / Montis

We have a small house and the listening area is 12x20' (which includes a dining table at one end). Speakers on the short wall, 5' out from wall, 6' apart, 2' from sidewall, listening position at 8'. Due to the layout of the house (and WAF), this is not going to change more than a foot or so.

System is ML Vantage, (2) Velodyne DD-15s, Audio Research LS17/VT-100mkii. Recently acquired a Mark Levinson 331 in a trade, but plan to sell it. I started thinking about getting speakers with a better bottom end and sell one or both subs to make more room/less clutter.

I've been considering replacing the Vantages with Summit/Summit X/Montis.

1.) I know this will help with the bottom end, but will it allow for elimination of both subs? one? 

2.) Will these panels be a dramatic change in quality in mid-bass and higher? Or just another "step up"? I'm assuming the larger speakers have the same sound signature?

3.) Also had thoughts of trying Wilson Watt Puppys in the same price range ($5-6k). I've owned almost exclusively panel speakers (Apogee, Soundlab, Magnepan) over the past 30 years. I listen to a very wide variety of music and understand the different nature of these compared to traditional driver configurations. Owned Aerial 10T for six months and was not so impressed with Krell amps, but the VT-100mkii sounded awesome. Ultimately I moved on to the Vantage and have been content for four years. Classical Indian, acoustical blues, jazz vocal, are quite pleasing on this system, but I sometimes yearn for more slam when playing, oh for instance, Led Zeppelin. Maybe the larger ML will help lessen this craving?!