I think they are trying to upsell you. I'd try them without first, then possibly consider adding a cheaper unit to get an idea of if you like it or not. The super tweeter and cap combo they recomend will have the tweeter producing noticable volume only in the upper half of the highest octive of music, and there really isn't much up there. I can't see justifying spending that kind of money on a expensive supertweeter that does little more than add some sparkle to the music, IMO. I don't see why you couldn't just supstitute the FT17H and mount it in the cab-way cheaper. Or if you want to keep it separate, why not stick it in a short peice of steel pipe on top?