I desperately need an easy to use blade sharpener and I use mulch blades which obviously have curves. I have tried grinding wheels and currently use handheld angle grinder but feel that I am butchering my blades. Please tell me what makes your product better than others on the market. Is the 8000 the only one that will sharpen the mulch blades, and if so, why is it more expensive by $400? I need the cost to be justified. Please respond! Thanks!