Subwoofer for Ayre AX-7e?

Though I am biased toward Vandersteen, I have to second Johnny's recommendation.
Your speakers are probably the weakest part of your system, and the M5 are the lower end of the Epos offerings. 
That being said, the Ayre integrated that you have is a very good unit and if paired with Vandersteen 1's would probably knock you out of your seat.
And, the price for a used pair is very reasonable.

I also am using the AX-7e in my office with a pair of Zu Omen Bookshelf speakers and HSU VTF-1 subs.
The Ayre handles them at line level with no problem.
When funds come available, I am going to get a pair of Vandersteen VLR's to replace the Zu's.
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@almarg .
My office rig is in a relatively small room (10'x10'), so I don't play music loudly and usually within a small range of volume. In any case, after setting things up the way I liked, I don't find the need to adjust the subs' volume. In fact, I hardly have them outputting, as the Zu's have pretty good bass output by themselves.
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@OP...
As others have suggested, contact Ayre for the best advice.
I am sure you will be impressed with the Vandy 1's. 
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@jackd ,
The Vandy subs use crossovers at the 80 to 90hz frequency, so will more than likely be able to work with just about any speaker.
The OP could use the 2wq's with his integrated if he sent it to Ayre to have it modified to include the crossover caps. But, it would make more sense to move to a pair of Vandersteen, as well.
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