Rleff, here is another option for your consideration - the Janszen zA2.1.
This is a seamless hybrid with electrostatic panels above 500 Hz and dual woofers below. I suggest this for several reasons.
First I have a pair and believe they are the best speakers I ever owned. They will provide the detail and clarity you are likely accustomed to with your M2s. But they have a smaller footprint and can be placed closer to the front wall than dipoles because the rear wave is fully damped (closed cabinet). Yet they are spacious. They will play as loud as almost any listener would want and are surprisingly full range with measured in-room response into the low 30s. Lastly they are roughly half your budget limit.
Good luck.