Joe,
You're welcome.

The setup you describe sounds good. It would seem to put you at 35db, and if there is any line loss, actually a bit lower. But boy, with a 75 ft tower are you sure you need an amp? (I'd kill for that size tower. We have heavy zoning against such things where I live.)

Next step, you have figure your Frensel limit... I think www.ydi.com has a nice online calculator for Frensel. We'll make a skunkworks RF engineer out of you, yet. :-)

Cheers,
Thorn