Schubertmaniac--- couldn't agree more with you about Maggies/SLs/boxes. I've owned Maggies since mid-'70s----most recently 3.5Rs (which I still have. HP likes 3.5Rs/3.6Rs when combined with a subwoofer, but if you start adding up what it costs to bi-amp, with the extra amps, interconnects, speaker cables, subwoofer, etc., as the monkey said when he peed in the cash register: "This is gonna run into money!" And fast!)----but the SL A-3s (same as M-2s, functionally) I bought about a month ago are in a totally different class. Transparency/natural timbre are strong points, AND they've got as much accurate bass as I could ever hope for. (Caveat--I listen to classical music almost exclusively----YMMV.) I've gotta say, however, that the Maggies perhaps do image a bit better, although I'm still experimenting with speaker placement.(Unfortunately, at least IMHO, there are more compromises in speakers than in any other component, except perhaps phono cartridges, the other end of the chain. Maybe in the future there will be one speaker that does it all, but that doesn't seem to be the case at the moment.) Can't speak for the Maggie 20s----I've never heard them----but I'm extremely happy with SLs. I've heard there is a long waiting list for any of the Maggies (about the same for SLs, also!).
As for box speakers, there are without doubt some excellent ones---- I'll be the last to criticize anyone's choice---- but to be perfectly honest, the only ones I've "listened to" in some 25 years were a pair of Revels in a salon when auditioning a Sony 9000ES recently. The only demo classical SACD they had was of Glenn Gould, so I couldn't tell much about image/soundstage, etc. I guess Maggies and SLs have simply convinced me I'm a planar nut.
BTW----in my limited experience, some SL dealers will knock a bit off the retail price----seems to be discretionary. Also, beware of some of the used SLs on various classifieds. From what I've heard/read, Dr. West, the SL designer, is constantly "tweaking", so what seems to be a bargain may be otherwise, depending on year of manufacture, fixes/upgrades that have been done, etc. There have been many improvements over the years. Get serial numbers, contact the factory, and they can tell you about the history as they know it.
Jim