I am looking to buy a gps system, but I have a low budget. I want Trimble, but I have a few questions on the R8 and R10. The R8 model 3 is the closest to my budget with out going to outdated. I need a system that will last me at least 8 years. Will the r8 still be good that long? I work under canopy often which I hear the r10 is better for, or how does the r8 work under canopy? I really like the new feature that the r10 has with the xfill. Would the xfill still work on the r10 if i used an r8 as base? Or what would be the down side to having an r10 as rover and and r8 as base? How much difference is there between the r8 m3 and the r8 m2?