Just as a bit of fun and something else to play with, I've been using one of these for a little while: http://www.ebay.co.uk/itm/Little-Bea...4AAOSwZ4dZEtWt
It's dirt cheap, but well built and looks pretty funky and it sounds way better than you'd expect. It works a treat with my Quad 306. I'd imagine it would pair up well with a Leak Stereo 20 as well. At twenty five quid you can't go far wrong really, even if it's just kept as a back-up. You do have to wait for it to arrive from China. Mine took about three weeks. The seller is reputable.
These are available from various far east sellers and 10k, 20k and 50k options can be found. Mine has the 20k pot.
.