Martin Logan Floorstanding Motion Speakers: 20 or 40?

Hi folks, 

I had a question for those who've experienced the Martin Logan Motion speakers. I am looking to purchase a pair of good floorstanding speakers. After reading through reviews of various speakers (Klipsch Reference Series, Infinity Reference Series, ELAC, Bower and Wilkins 685 S2) I called the local Magnolia home audio expert. He recommended trying the Martin Logan Motion 20 speakers. 

I went back and read the reviews on these. They are generally quite favorable and I'm willing to take the plunge. My question is: should I go with the 20s or the 40s? I live in an apartment and don't want to crank up the volume too high. At the same time, I would like to purchase speakers that led me enjoy hi-fidelity, clear music at a lower volume with adequate (but not booming) bass support. If anyone has alternative recommendations, please feel free to share those. 

I already have a Klipsch quintet home theater system and will be looking to replace the two front speakers with the floorstanding ones. I use a Polk Audio PSW10 subwoofer and a Sony receiver. (The receiver will also be replaced by a Marantz receiver; either the SR5010 or the NR1606.) 

Thanks for your time!

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I spent a couple days listening to all the motion series and I also live in an apartment...I felt the most musical was the 35XT...The 40's bass would be unruly in a smallish apartment and neither the 20's or 40's imaged as well as the 35XT(bigger tweeter?)...
I happened to be in a Best Buy and went into the Magnolia Sound room a couple weeks ago. I was curious to see how the Martin Logan ESL's compared to the Aerius-i I had years ago. The guy at Magnolia switched from the ESL to the Motion 40 to the Motion 20.  As expected the ESL was the best and sounded very clear with good resolution. The Motion 40 sounded a close 2nd but the Motion 20 sounded very "muffled" compared to the 40. The midrange on the 20 sounded congested and it did not have the resolution or detail of the 40. Take this for what it is worth because it is just my opinion after listening to only 1 song switched back and forth between the speakers for a couple minutes. I didn't buy anything but my choice would have probably been the Motion 40. Good luck.