WOW! I am stunned!
I had no idea that Apple has never seen fit to put a balance control on any of its iPod products. Incredible. Especially since a lot of the people that are complaining about it are people with hearing impairments in one ear. I don't know what to say. I use an iPod Nano in my car which I enjoy, but I can't believe they have never added such a simple adjustment. Given there are people who have a legitimate physical need for it, I don't understand how they can possibly justify that (especially since my Nano has about a bazillion other useless settings on it!)
As to the SpAudio amp, as far as I know, the only HS tub that requires the amp to be placed behind a fixed panel is mine...an Envoy. I'm not sure, but I think your amp is in the main equipment bay of the tub. Have you asked your dealer about this balance problem?
Rich