I have a pair of custom speakers similar in design to the Legacy Focus using Eton drivers (tweeters/midranges/midbass drivers) and 12' Peerless/NHT woofers. I've been biamping these for years with a JAS Array 2.1 driving the midbass on up section. For the 4 12" woofers, I used several amps with varying degrees of success. I had a Consonance Calaf briefly (integrated amp)and this was exceptional driving the woofers but I couldn't justify the $1800 I spent on it as a woofer amp so sold it. I've used a Hafler P3000 and this produces a punchy and weighty bass, a great deal at the regular Ebay prices. Even better, and about the same price, are the Face Audio professional amps. I'm using the 250 watt model presently and find it better than the Hafler, but it's also an extra 100 watts/channel.
I had a Wyred4Sound ST-500 for awhile, driving the speakers full range. This digital amp produced a punchy/dynamic bass but it didn't have the weight or authority of some other amps I've used. The Calaf killed it in bass reproduction and an Adcom 555 II I had on hand bettered it in bass as well. I think the Hafler/Face Audio amps are better as well but it's hard to say for sure as I've never ran those amps full range with these speakers.
In another system I have a Cambridge Audio 840W. I haven't used it with these speakers but I find this amp to have really wonderful bass, very tight and dynamic but also with plenty of weight. I reminds me of a Krell KSA 100S I had years ago (as far as bass goes that is). Overall, I really like the Cambridge amp. See the TAS review regarding their impression of its bass capabilities. Thanks and good luck!