Hi Mike,
My first experiance with a REL Strata III sub scared me. I thought I had bought the wrong speaker. It really sounded whooshy for the first 24hrs and proceeded to get better over the next week. Be calm... they are the best! I have bought many more up the model ladder since and love them.
Change the power cord out. It REALLY effects the RELS. I have a forum post regarding the REL subs if you are interested. Drop me an email.
Dan
dedicatedaudio.com