If your only using the dozer 20 hrs a year then its time for the dozer to go. I just let my 450c trackloader go, was putting maybe 30 a year on it. In its place I picked up a gehl ctl 70, or takeuchi tl140, they are 10k pounds and 80hp. I've put about 30 hours on it this month backfilling and grading around a new house, I thik it was a wise move.
I would not consider the ctl a direct replacement for my 550g though, they both can fine grade, and for some things its faster to use the ctl cause it can carry dirt to fill a hole, but the 550 can burry the ctl in heavier work, and the ctl isnt as nice when finishing a slope, at times it wants to slide as soon as the bucket touches something.
My concern is the cat having enough lift and breakout, does it have highflow, 2 speed, or a cab? Any attachments come with? Do you already hve a wheeled skid? Also do you have another dozer? I'd have let the 550g go for the ctl if I'd have had a winched 700 or 750 as well as the 550, I just can't live without the foresty dozer for some of my work.