Regarding subs...
There was the suggestion that an M30.1 plus sub would be ideal. I've wondered about this for a while. Someone on the UK forums has been trying to do this but having problems with integration. Will he ever succeed?
When you have a small room, getting the bass right is like finding a suit that fits perfectly off the peg. In all likelihood you are going to need the trousers shortened or something taken in.
I suspect what is really needed is an active crossover, so that you can covert a two way into a proper 3 way. I learnt this when trying to integrate a sub with the 63s, with little success. Then I got the Gradient sub-woofers, with active crossover, using a separate power amp for the subs. It massively opens up the 63s and gives controlled deep bass in a small room. However it was visually overwhelming, and sonically I really needed to be further away for it to properly work.
I sold the Gradients last week with a heavy heart. If I had a big loft apartment, that would probably be my ultimate system.
It has left me wishing that it was easier to implement this kind of active crossover system with more conventional speakers.
I know a couple of guys in the UK who have developed an active bass system that is meant to work with small monitors in the LS3/5A mould. It is a tower sub-woofer that sits perfectly under a mini-monitor, and they have built an active crossover and power amp for the subs. So you can use you own amp on the monitors, and it makes the main monitors more efficient, so you can use a valve amp with LS3/5A easily.
They demonstrated this system a couple of years ago at a show with some Spender LS3/5A and the Murphy CAOW1. It completely floored me how open and rich this sounded. They played a master-tape copy of Sonny Rollins' 'Saxophone Colossus' and I've never heard such ghostly realism in the reproduction of a tenor. So it was as much about how it liberated the mid-range as supported the bass.
The problem is that they have only built 2 - for themselves! It's not been marketed as they are both very busy.
It has left me wondering how you might use an active crossover with a superb 2 way like the M30.1 and a pair of subs. The key would be setting the crossover above the port output, which is where everything gets muddy. The guys that developed this system are firm believers that ports are the worst compromise in speaker design, and after a year with electrostatic panels I'm coming round to that way of thinking. Saying that, I suspect I will accept a compromise, like most of us do.