Well, if you have a little saw, you could swap the 50cc for a 60cc if that's what your heart desires. Personally, I'd probably keep the 180 and the 5100 and add a bigger saw. Bigger than 60cc. Something like a Dolmar 7900 or a Stihl 440 or 460. But, that's just me. I cut hardwoods of various sizes, up to 40" (not very often, but it happens), I like having several saws on varying size classes so I always have the right tool for the job. I also like swapping saws when a chain gets dull or the saw runs out of gas. Just my personal preference, I guess.