I can personally echo what everyone else has suggested. We are using a Vertex VXR-7000 (they can be had for around $700 on ebay with a duplexer) running 30 watts out the duplexer.
Original location was our home at 40 Feet above the ground, range was okay, it covered 90% of what we wanted (about 15 miles on mobile and 5 miles depending on portable).
We relocated to a commercial site at 220 feet. Now I find were mobile was sketchy at best, portable is like an S3 (some hiss in the background) and this is in basements or 12 miles from the repeater in an aluminum sided house.
We are running 7/8 hardline, 10dbd collinear omni but mount on the east side of a tower (which is not towards my optimum coverage want (I would probably be shocked at a pattern that covered what I wanted)
Long story short, height, height and more height. Little 20 watt repeaters at his location on the tower scream!