Subwoofer for Tannoy Autograph Mini

Depending on your local, and prices I would recommend the MJ Acoustics range. They are very simlar to the original RELs, strata and studio, but are more reasonably priced. I am running a MJ Acoustics Ref 150 MkII with SET amps and horn hybrids, and they keep up and blend really well. A superb combo for me.

http://www.mjacoustics.co.uk/

If you want augmentation only, any recent small REL would do nicely (Britannia 3, R-305); if you want to high-pass the Tannoys at a relatively high frequency, say 80Hz to 100Hz, you need a transparent active crossover such as the Hsu Research high-end crossover and a pair of very fast subwoofers such as JL Audio Fathom f112 or ACI Force/Titan XL. There are plus and cons to each solution, of course.