I've got a Retevis RT97 10 watt repeater hooked to the MA09 antenna that came bundled with it. The antenna is 43' AGL on the highest point of my property. I was able to communicate with a friend on his mobile rig over 11.5 miles away. Having said that, there are valleys much closer to me than that and no communication is possible to those low lying areas. Still, I can get several miles in all directions with this setup. It runs off of a 30 amp-hour battery connected to a 100 watt solar panel.
Also, not that you need more power, but, Retevis announced the RT97L which is an updated version of their portable repeater. It is rated at 25 watts. It is supposed to be in stock on April 4 this year. If nothing else this may allow you to buy an RT97/RT97S at a discounted price, maybe even get a used one from someone that is upgrading.