I've done research into building the EBS (142.5L) vented Shiva subwoofer. I will be picking up the mdf next weekend and I have a few questions. I am in Canada and Creative Sound Solutions does not sell the AVA 250 ampflifier. Adire Audio sells it for $179 US, while Parts Express sells a 250watt amplifier (4 0hm) for $128 . http://www.partsexpress.com/pdf/300-796.pdf Would the Parts Express amplifier be a good choice or should I go with the AVA250? Should I use polyfill? I don't see any reference in the plans that refer to using polyfill and I was wondering if anyone uses it. Also, what should I use to seal the joints? I have read that you should not use chaulking. Thanks for all your help.