I would like to know if there is a good quality amplifier on the market that is reliable.
They can always be damaged by a nearby lightning strike. So make it easy to replace, like at the foot of the pole. Amplifiers using PGA103+ can take almost any kind of huge signals without loosing performance and are extremly low noise. Get that suggested FM trap filter, they are always good to have and make the amplifier box big enough to have room for it, if needed to sit between antenna and amp. I live 8km from tv and radio masts, probably the biggest and most powerful in my country, and don't need the FM trapfilter between antenna and a PGA103+ amp but some receivers need it so I use it in front of a splitter.
RG6 are almost as good as LMR400 and probably 10 times cheaper and more easy to install. They use RG6 for sat dishes at 2GHz. Whatever antenna you get it will not hold 50 ohm over your frequency bands, and not even your receiver will be 50 ohm, so no big deal if the coax are 75 ohm. If you have an antenna mounted amplifier and then a 5$ isolating splitter at the receiver it will keep a constant impedance to the coax doing a much better job than with a 50 ohm coax without amp and splitter.
If you are not too concerned about the 800MHz band then any antenna will receive strong local systems when you have it that high up. If you have used the RG58 at those frequencies then the signal have probably been reduced 5 to 10 times at the receiver.
/Ubbe