Hey man, I've got my buttkickers mini's dialed in REAL well now. They aren't for everyone, but time delay is everything. I found out that they need to be set to about a 4 foot distance in my room to match up beat for beat. I had three guests in my theater in the last week. One said he was ordering them the next day. One liked them a lot, but didn't think they were actually necessary, and one guest didn't like them. So again - not for everyone - but it makes a HUGE difference to have the distance/time delays set appropriately. With my mini's I've also found a slight rolloff starting at about 35hz is good to protect the buttkicker mini LFE from rolling off. (though I'm putting a LOT more power into mine than you are with your 300 watt amp for three.) I'm still playing around with my low pass filters on the Inuke DSP 3000 amp to determine exactly what I like. I had it full range up to the AVR subwoofer 2 crossover of 120hz, but am trying 60hz now in the INuke DSP. I think a bit higher than 60hz is probably appropriate. Still trying to get that dialed in.
Anyway --- good luck with your sale.