What are some of the downsides of owning a Magneplanar .7 or 1.7i ?

[Magnepans] Lack of Dynamic Range . If you play Classical Music is a problem with rock/pop is not.

Not in my experience with my 1.7s, but then I cheat a little bit. I have sandbags on their feet to dampen vibrations, use the tilt-back spacers to energize the room better, and have them perfectly mated with a pair of small, fast powered subwoofers (1400w peak) to fill in the 36-50Hz region. The panel/sub coherence popped into focus when I dialed in the continuous phase control. That adds a lot of power and dynamics. I use this rig almost exclusively for LP playback. My amp is rather modest by today’s standards--a Perreaux PMF-1150B rated at 100 wpc into 8 ohms. Factory specs didn’t specify output ito 4 ohms, but with the results I’m getting, it must put out close to 200 wpc into 4 ohms.

Anyway, this rig does dynamics gloriously. I love playing bombastic large scale orchestral works--Russian showpieces, Holst’s "The Planets," Beethoven’s Eroica, and big band--Buddy Rich, Count Basie, Harry James on Sheffield D2D, etc. When I play these records the dynamics knock me around the room. The dynaimcs really took off when I acquired a MAGI Phonomenal phono stage--all tube handwired PTP. I also have the matching line stage. Together they transformed my rig.

... Going from my 1.6 to proac d48r has been a revelation. Dynamic range is definitely a component of emotion. While the maggiea served me well, they are no match for my new speakers.

That’s hardly a fair method to make a general characterization of Magnepan products. The 1.6 is a 20-yr-old design and was discontinued at least seven years ago. It is not representative of Maggie’s current product line. The 1.6’s replacement, the 1.7, was such a quantum leap in performance that the technology was applied throughout the line: the 3.6 became the 3.7, the 20.1 became the 20.7, the the .7 was introduced as well. I can also attest that with the right setup and appropriate-sized room, the Mini Maggies are also *very* dynamic.

And let’s not forget that your new speakers retail at $10,900. Let’s hope they sound better than 20-yr-old $1500 speakers. You could buy a pair of Maggie 3.7s plus $5500 worth of subwoofers for the price of your Proacs,

Most everything stated above is accurate so I won't repeat.  To me the most important aspect of owning Maggie's comes down to musical taste.  If you want to blast hard rock and such I'd look elsewhere, however, if your tastes run more towards Jazz or softer rock like Steely Dan, Maggie's are capable of things that box speakers simply can't do.  Admittedly they need lots of current and placement wise they need a minimum of 3 feet behind them.  I would also add that stiffening the panels will pay dividends, there are several ways to achieve this that I won't get into but search the web you will find Maggie owners who are doing this.  I've seen many an audiophile come unglued the first time they heard Maggie's, they're certainly not for everyone but for those that love em' nothing else will do.

Sunnyjim (the OP) posted in part:

I currently have a pair of Golden Ear Technology model 7's....which I like and generally sound good However, I would like to confirm what a planar design brings to the table in sound quality. I have read many times about the box-less sound provided by this design, and its wide sound staging and low distortion.

I think I have enough power with BAT VK-200 amp (100RMS) to drive the .7, but not sure that is enough to drive the MG1.7i. to higher volumes The pre-amp is a Conrad Johnson PV-14SE.

3-1/2 years ago I did a fairly comprehensive search for a pair of $2K floorstanders. Final contenders came down to the Goldenear Triton 7
and the Magnepan 1.7. I took my wife along plus one of her favorite musical works, the cantata "Elijah" by Mendelssohn. She has a strong history in vocal music, especially ensemble, oratorio/cantata, and opera.

I was looking for a tie-breaker. There were things I liked about the Triton 7s, including price ($1400), small footprint, and top-to-bottom tonal balance. But I didn't find it quite as engaging as the Maggie 1.7s, but I wasn't sure what it was.

My wife knows "Elijah" backwards & forwards. We played Elijah through the TRitons, and then the Maggies. There was the tie-breaker. There are passages in Elijah that have EIGHT-part vocal harmonies. She couldn't hear them all from the Triton, but easily picked them all out through the Maggies. Inner detail, anyone?

When I asked if she was OK with the Maggies' imposing size (5'5" tall x 19" wide), she said, "Are you kidding? It's the sound that matters." And we took them home right then and there. Did I get the world's best wife? I think so.

The more I listened to the Maggies at home, the more extraordinary they revealed themselves to be. First of all, the Maggies showed me how noisy most box speakers are--how much vibrations, resonances, and pent-up and released backwaves obscure inner harmonies and details that otherwise make the music come alive. I am continually enthralled by the effects of subtly applied background vocals that largely go missing on other speaker types. I also found that the dipole pattern with out-of-phase backwave does wonders for taming the 100-200 Hz hump that seems to plague in-room response curves with conventional speakers

Also, SunnyJim, I have a listening room similar in size and feature to yours, including the room dimensions and the open architecture. However, I even have a 15' cathedral ceiling. My amp even has the same power rating as your BAT--100wpc into 8 ohms and 200 wpc into 4 ohms. The 1.7s are easy to drive with this amp, and the speakers fill the space with clarity and dynamics. You may want to get a fast sub or two to help the bass energize the room.