What is the simplest cheapest crossover to use so I can use my 2 monitors with my LMS sub in a 2-channel system? I have an old Classe' Audio preamp that has 2-outs that I have been using. I use only a Squeezebox as source. Have a Rane PE17 and/or MIC22000 for HPF on the sub. I use a Face Audio amp for the sub, and I have a 2 channel amp for the monitors. I just want to send below 80-100Hz to the sub.