Sealed subwoofer for ESL-63

I am looking for owners who have successfully integrated their QUAD ESL 63s with a subwoofer.

I recently bought a used pair of QUAD ESL63 and had them rebuilt, panels and electronics, this is my third pair. I have had several monkey boxes in between - Aerial 10T, B&W, KEF, IMF, Tannoys, Proac, Goldmund, Falcon Acoustics kits, etc - but the 63s are very hard to live without when you know what they can do.

My problem is that I am particularly fond of large-scale symphonic works such as Wagner’s The Ring , Beethoven, Mahler, Strauss, etc. but the 63s are very special and very frustrating used full range, they have limited bass and dynamics.

I am retired now and have a fixed income so I cannot keep doing what I did for fifty years, buy, experiment, trade and sell.

I would like to keep the cost of the sub to $1K max for a good condition, one owner unit.

Best regards,