Amplifying TV antenna signal

Ladies and Gents:

I just put up a new super-duper TV antenna this weekend.  It's a
Channel Master Ultra-Hi Crossfire 3671, which theoretically has a
Reception Range of 100+ miles for VHF/FM and 60+ for UHF.

The ground elevation of my home is approx 680 feet.  The tower is two
standard sections of Rohn 25 plus the top section.  The rotor is two
feet above the top section, with the horizontal section of the antenna
being 4 feet above that, for a total of 36 feet.  That puts my antenna
at about 716 feet above sea level.  I have a 300-75 ohm balun attached
to the antenna with about 75 feet of coax to the TV.

There are still a few UHF stations I cannot pull in and I'd like some
hints.

One UPN affiliate (WRJM) has a tower 1560 feet above sea level
broadcasting at 2.8 MW on channel 67. According to an online
calculator, it is 73 miles between my town and the tower.

Another UPN affiliate (WBAM) has a tower at 1,030 feet [Height Above
Average Terrain (HAAT)] broadcasting at 1.45 MW on channel 68.  The
distance is 53 miles.  This one is just strong enough to kick the Blue
Screen off on my TV, but no picture or sound.

A PAX affiliate (WBMM) is 51 miles away broadcasting at 2820kW on
channel 22. I can't find any tower information on them.

Question is:  what can I do, if anything to pull these in?  I've seen
pre-amps on the web.  I don't want to bring this tower back down, so
I'd like to amplify it inline if possible.

Thanks!

Steve Thomas