A hifi bake-off friend has stacked 57s in a pretty large attic-like room. He has single 57s before and the transition was noticeable by all the group. Unusually, he being an old school valve collector and expert on most things valved, powers them with a 1960s Sansui amplifier; quite rare in this country.
Interesting re. the comments of pros and cons of successive Quad ESLs but esp. what has been used to power them. I use EAR 100 W mono's for my 2905s; or did, and hope to again. The EARs are not lush in the remotest way; the 'valved equivalent of s/state', has often been bandied about. The late lamented T de P used 63s in the designing of there 509 mono's and much else. Surprisingly, perhaps, they also sound superb with my PMC floor-standers, which have to be diametrically opposed to the ESLs in presentation. Maybe these PMCs revel in the very slight valve effect whilst retaining all their detail, dynamics and soundstaging.
What puzzles me is that all or most comments above mention the smaller versions (988/2805/2812) of Quad's ESLs, but the footprint of these is identical to that of their bigger brethren. Why would you prefer the smaller on to the one giving that extra bass extension? Maybe cost? I dunno but if Quad did one even larger (with a wider fre. response, of course), I'd be in the queue as height of a spkr is on no concern, surely; esp. in properties with older ceiling heights.