I've been biamping a pair of DIY speakers that are similar in design to the Legacy Focus using a pair of Peerless 12" woofers per side as well as Eton midbass, midrange, and tweeters. The bass drivers seem ever so slightly less efficient than the rest so biamping was the only way to get the sound I was looking for, otherwise the speakers seemed bass shy and 4 12" woofers shouldn't sound that way.
My sources are mostly cdp or universal players though I occasionally hook up a Revox B261 tuner. All of my sources have at least 2 outputs, the universal players having the stereo outputs as well as the full range FRONT outputs for surround. The tuner has fixed and variable outputs. I connect the stereo outputs to my main amp (presently a JAS Array 2.1 integrated using 805 and 300B tubes with a passive linestage) and the FRONT outputs to the amp I will drive the woofers with. In the past, I've used an integrated amp for this purpose, a Consonance Calaf, with great results. Presently I use pro amps, having both a Hafler and a Face Audio that see duty (only 1 at a time).
You could go from your source(s) into your preamp with 1 output and and use that to drive the Audio Note amps and into a pro amp with attenuators with another output on the same source or an integrated or get another preamp that will drive a separate amp for the woofers. If your source(s) doesn't/don't have 2 outputs, you could get the same result using a Y-cable. You don't see many high-end Y-cables out there so you may have to build your own or have someone build you such a cable. I've used soniccraft for this and their work is very good and affordable.
I've always found the bass to blend in well with rest of the range only standing out if turned up to high like any subwoofer. You should be able to get not only acceptable results but much better results than biamping with another pair of the Audio Note amps as you can use whatever solid state amp you wish. One issue with the pro amps though is that most use XLR and don't have RCA inputs. Just use XLR to RCA interconnects. If you have a pair of unbalanced interconnects that you like, you can always have XLR's installed at one end. Good luck!
My sources are mostly cdp or universal players though I occasionally hook up a Revox B261 tuner. All of my sources have at least 2 outputs, the universal players having the stereo outputs as well as the full range FRONT outputs for surround. The tuner has fixed and variable outputs. I connect the stereo outputs to my main amp (presently a JAS Array 2.1 integrated using 805 and 300B tubes with a passive linestage) and the FRONT outputs to the amp I will drive the woofers with. In the past, I've used an integrated amp for this purpose, a Consonance Calaf, with great results. Presently I use pro amps, having both a Hafler and a Face Audio that see duty (only 1 at a time).
You could go from your source(s) into your preamp with 1 output and and use that to drive the Audio Note amps and into a pro amp with attenuators with another output on the same source or an integrated or get another preamp that will drive a separate amp for the woofers. If your source(s) doesn't/don't have 2 outputs, you could get the same result using a Y-cable. You don't see many high-end Y-cables out there so you may have to build your own or have someone build you such a cable. I've used soniccraft for this and their work is very good and affordable.
I've always found the bass to blend in well with rest of the range only standing out if turned up to high like any subwoofer. You should be able to get not only acceptable results but much better results than biamping with another pair of the Audio Note amps as you can use whatever solid state amp you wish. One issue with the pro amps though is that most use XLR and don't have RCA inputs. Just use XLR to RCA interconnects. If you have a pair of unbalanced interconnects that you like, you can always have XLR's installed at one end. Good luck!