The way I see it the price reflects the number of people that want this. While it may fit good to your need because you don't have to pay $100 /hr for a truck to move it around your place, most buyers do. So resale will not be as good
Also if it needs repairs are you going to have to float it to a shop? Getting it on a float can be a major job if its disabled.
Fixing it yourself requires some serious tools, crane/hiab for lifting parts. Even fixing a derailed a track can be a major job.
I have done it on a 350 jd crawler, it involved 2 men come alongs chains and 2 hours work. crawler tracks can come off easily, compared to skidsteer tire tracks.
If you have any soft ground, you would want to be vary carful about getting stuck, because you will need another 6 to pull you out.
Of course ground speed and turning around will be slower.
On the plus side it will push out a bigger stump, or move a bigger rock, I'm not sure how big yours are, but remember that all machine regardless of size have limits, I'd say about 18" stumps (in out part of the country) it the limit. That why they make 7s, 8s, and 9s with rippers. Cat equipment generally has good parts availabilty.
A 6 is a good chunk of tractor, my father built his logging roads between 1965 and 85 with a TD9 International and a jd 350, which would be like a d4 and d3. (This was on a island and that was the limit for the barge to float across the lake) He still has both, the 9 needs engine work, and can't be given away, (blade is worth more then tractor, its a 50's era) and the 350 (early 70's) he still uses around the farm, but in lots of ways a midsize bobcat will do almost everything the 350 can and quite a few things it can't with a different attachment and the better visability. Though the longer track frame on a cat excells at making a level road or grade.
I know he used to bury rock piles with it, dig basements what ever, but the last time he cleaned a field, he had a excavator come it for $85 a hour, which was alot quicker then the jd for pulling stumps and buring rocks, they done a ditch at the same time.
If you have alot of heavy work, this may be the answer, and keep the 610 around for the small jobs. But when you done with it it will be alot harder to find it a new home. If you have you money out of it and then some by this point then it was a good choice
Regards
Ken