Do larger planar speakers produce more accurate sound?

The Levinson HQD system was something I heard MANY years ago, so I cannot say how it would compare with other systems.  It was more than stacked Quad 57s; it had a 24" Hartley woofer and Kelly ribbon tweeters.  At the time, I thought it sounded okay, but not decidedly better than anything else I heard.  More recently, I've heard stacked Quads assembled by MyEmia that incorporate bespoke tube amps that take advantage of the high impedance of the electrostatic panels by not utilizing the kind of output transformers one would normally need to lower the output impedance of the amp to match conventional drivers; the stacked Quads delivered surprising volume and bass impact for a speaker otherwise known for their deficiencies in these qualities.

The big Soundlabs are indeed very nice sounding speakers, but I would not pick them over the better horn systems I've heard (custom made speakers).  I would also like to hear the new Beveridge hybrid electrostatic/dynamic systems; I heard the originals and like it except for the overblown bass response.  

I've owned a few planars over the years-Magneplanar i, Acoustat 1+1, Martin Logan Quest, and I've heard many iterations since.  I like what good planar speakers can do--create an enveloping soundstage, deliver clean and clear sound without being unduly harsh or artificially "forced".(no sense of unnatural edginess to the attack of the note).  But, like all speakers, there are some areas where they don't quite do so well, such as the requirement to be playing fairly loud to come to life (of course there are exceptions, like the Quad 57), and they are not as dynamic sounding as good horn-based systems.  The main issue is that most are not quite efficient enough to play well with the kinds of amps I like the most--low powered tube amps. 

If by “clarity” you mean an absence of resonance that makes for a murky or muddled sound, panels and compression midrange drivers can be very good.  The very best compression drivers, such as those made by Western Electric, International Projector Company, YL, G.I.P., Goto, manage to substantially avoid nasal resonance that color some compression drivers and deliver clear, detailed and well textured sound with a sense of ease.  These drivers must be matched to very nimble and clear sounding woofers.  The woofers that seem to work best have light cones, and pleated paper surrounds.  The downside to such woofers is a limited excursion that mean they don’t deliver extremely deep bass.  This kind of bass is similar to that of large panel speakers which also don’t go extremely deep.   

It depends on the amp, of course, but many single ended amps and pushpull amps using just a pair of tubes like 6L6 or KT-66 deliver a full, lush sound without sounding muddy or sluggish.  Within their modest power levels, they are quick and dynamic and the sound is "dense"--harmonics are complete and realistic and not lean and thin.  I don't like most high powered tube amps with multiple KT88, KT120, KT150 because they tend to have a hard and brittle sound--the initial attack is artificially edgy and not as natural sounding.  Most high powered solid state amps sound lifeless to me at modest volume levels.  There is also an artificial sounding edginess to the attack of notes that  makes them a little bit brittle sounding or as some people put it, there is a "glassy" sheen that seems to be always present..  A good tube amp sounds relaxed and not edgy, yet when the music calls for it, they sound lively and deliver dynamics without sounding hard.

A decent 40 watt amp (e.g., Synthesis A40) should work with the majority of speakers, but, some panel speakers might require a bit more, depending on the setting and circumstances.  I don't rule out ANY speaker type, and certainly there are many that I enjoy even when driven by amps that are not my personal ideal amps.  It is just a part of juggling different strengths and weaknesses and making the right compromises.  I could easily live with something like the 30.7 Magnepans and an Ayre amp, although I still prefer a good horn system and my 5 watt tube amp.

Some do have that sort of nasal coloration, some do not.  I am not a fan of most of the current production compression driver systems (e.g., Klipsch, JBL), but systems made with some very special drivers from the like of Western Electric, International Projector Company, Yoshimura Laboratories, G.I.P. Laboratories, Goto, ALE, and Cogen, for example, coupled with the right horn can sound great and not sound like megaphones.  It is the bane of serious horn fans that the most popular and common horn systems, like those from Klipsch, JBL and Altec, do have that tendency if one does not work to reduce that problem and select the right components to complement these drivers.  It is also VERY unfortunate that the best of these drivers can be extremely expensive.  I have a fried seriously looking at a single $14,000 driver which he would buy on-line in a heartbeat if the seller would do something as simple as take a dc resistance measurement.