Great! My amp I used didn't add that much for the UHF air band, but the VHF civil, and military was phenomenal. Sorry to hear it didn't work as much as you though!
I do know Angle Linear does have quite a few UHF ones, NASA uses them, but they are about $200... for that price, I would go buy a new radio and antenna! I'm thinking about going and buying the GRE PSR-400. I do have a 155/800 MHz Public Safety antenna up, but It really does no good..... there is no 800 MHz within about 100 miles. I do use it for air band, and public safety though.
Let me know if you have any more questions,
Caleb