Which magnepan

The MG 1.7 has some stiff competition in the Eminent Technology LFT-8b, another speaker employing magnetic-planar drivers. The ET also contains a ribbon tweeter (10kHz and up) and dynamic woofer (180Hz and down), and is about the same size as the 1.7---13" wide, 5' tall. Occasionally offered second hand for around $1500, it plays a little louder than the 1.7, with deeper bass and a less "wispy" tonality. Instruments and voices are reproduced with more body and weight. A great value.

I've been wanting to hear them too. They have like 3 dealers.

I have my 1.7 set up in a room by 14 by 20 and it works very well.. Had MG11b's and SMGa's set up in the same room. Just did the crosser upgrade for the 1.7s and have about 10hrs on them.. all I  can say is wow.. will be posting pics and a write up soon.. 
Get the 1.7 .. upgrade the crossovers and you'll be very happy you did.

I owned 3.5Rs and could never get past the door size room blocker physical size.  I tried a wide variety of amps, both SS and tube (Rogue 150s), but found them hard to drive.

I supplemented the bass with 2 SVS subs (one Ultra and one Plus). Eventually I replaced them with Emerald Physics KC IIs, which are easy to drive 94dB, the bass is good that that I no longer use my SVS subs.

I ordered the KCIIs with the WireWorld OCC internal wiring upgrade (+$500). They include this wire in their more expensive speakers, but mine was a first to put it into the KCIIs. I was told by the assemblers that the improvement (by comparison to the basic wire) was amazing 

IMHO, they are well worth the stretch

In your price range I agree with those that recomment the 1.7 series.