If you are going to be mostly finish mowing your 3 acres I would not go as big as the
B7800 myself. I say that as the owner of a
B2910, which is the same tractor with a few more frills...
You might even consider a
B7510...I have pretty much concluded that a
B7510 size machine would be about perfect for my 3.7 acres now that I have most of the heavy work done here.
The key is mowing. The
B7800, being larger has the opportunity to do more damage to the lawn than a lighter weight tractor would.
I have a
BX2200 that I use for mowing, but actually when dry my
B2910 with a RFM did as good a mowing job in my opinion. But I don't have a show lawn, just a yard.
The problem is that price per pound goes down as tractor size goes up. We all want to get the most for our buck. But bigger is not always better. It is a hard call and each of us must decide what is best for us. And this is hard to do without personal experience to fall back on.
Myself, the best thing I could have done was move up from a
B2410 to a
B2910 on a whim at the last minute. But I followed that up with the purchase of a smaller
BX2200 to so smaller chores and grass cutting...there may, or may not, be a message here.
I had the experience of meeting a neighbor (fellow TBNer that is not too far from my house) and he had a
B2400, that is I believe the same size as the
b7610. It did a great job of mowing with a mmm on his 3 acres (or maybe a little less) so the
b7610 may work for you just fine.
It all depends....but for my property, as it sits now, if I had to have only one tractor it would be smaller than a
B7800 and larger than a BX...
Edit: OPPS! You said mowing 3 acres, but your profile says you have a total of 18 acres to deal with...that is a different picture...maybe the
B7800 would be the best compromise machine in that case...