Hello;
Can't resist my two cents on the amp issue. I would much prefer a 60 foot tower with a nice six element beam. Unfortunately, it is much easier to buy an amp than erecting the tower. If an amp isn't overdriven a signal isn't to wide. As for tvi type interference, true an amp can aggravate that problem. I found that going from 100 to 500 watts gives you about an extra s unit.
Richard