From my experience with the LRF 800 it will not do much better than what you have, you can expect 450 to 500 yards consistantly. About all I could ever get mine to range at 700 to 800 yards was a cedar tree, if the sun was not too bright. I also tried an LRF 1200 and was not impressed with it either.
I went with the Swarovski unit not long after they first came out. It claims to have a 1500 yard range. I have ranged deer and elk with it at well over 1000 yards, and a tree next to a deer or elk at 1500 to 1800 yards many times. If you steady it on rest of some kind it will range trees or hillsides at over 2000 yards. The Swaro unit is the only rangefinder I have had in my hands that will actually range day in and day out in field conditions as far (and farther) than advertised. I know they are expensive, but they work.