Hi,
You listen to a broad music styles.
Did you bought Quads at the end ? :-)
As for ESL2905, they are very expensive speakers.
It is tough to buy such an expensive speaker with no ability to listen to it
in the first place. I do like my ESL63, but it was bought 2nd hand and it is completly different price tag, so while i do like it "sweet spots" and they suits for about 50% of my music taste, i would not buy a 15000$ (or even 5000$) speaker that is not a good all around speaker for me.
Yesterday i heard again the MG1.6 and while they were more dynamic and had a better bass, i just can't compare them to my QUAD ESL63. ESL63s strong and weak sides are almost the same as of 1.6, with MG1.6 being a bit more suitable for "modern" music, but still not great for rock or pop. Still, for the strong sides, i would choose ESL63 any day.
I will try to listen to MG3.7 (some people suggest it might suit me as all around speaker).
There is another option of course. The one that seems to me the most logical to some extent. Have 2 pair of speakers I always thought of it as a non-adequate solution, because i don't have a big room space, hence 2 pair of speakers is not very convenient, but as far as i see buying good all around dynamic speaker (SF, Audio Physics, Dynaudio etc) might be pretty expensive and even then, i'm not sure, they could be compared to ESL63 in what it does well. So buying a moderately good dynamic speaker (even 2nd handed) for all the dynamic music and keeping the ESL63 might be a better (and cheaper) overall solution than going for a very expensive new ESL2905 (given it is still not that good for dynamic music) or going for very expensive dynamic speakers...