Almost a year ago, I picked up this '66 4000 SOS (pic below)that wouldn't move (a gamble) that including gas to go get it, and the parts/labor to eventually fix it got me a tractor that I don't really need for not too much over $3000....but that's an outlier I'd guess, probably a couple $K under the market for a tractor with less than 3K hours like this one.
Deals are out there if you're patient. My thoughts though are, need to determine your accurate needs....if you want to have a tractor to run a tiller in a garden...a 4000 and maybe even a 3000 are going to be pretty big, pretty heavy for most gardens, and a tiller that you won't destroy is going to come with a hefty price tag.
I'd say your 8n maybe isn't the top of it's game, and there are some shortfalls of that tractor you're now seeing.
I think you also need to determine how much your time is worth. You can mow 32A, or even your 7A orchard 5' at a time, and get it done...can also mow 15' at a pass in less time, but that takes a bigger tractor, bigger mower etc. You eventually pay for that time somewhere. Even stepping up to a 4000 sized tractor, you can pull a 6-8' mower easy enough in about all conditions, or a bit larger if you keep things short and mow regularly.
A 4000 is a nice sized tractor for use outside of the yard, but having mowed parts of my yard with mine and a flail mower, it can leave tracks. I do use it to plow/disk our garden, but could get by with less if I had it. Unless you're using it heavily, I wouldn't be too afraid of a 3000 for light/occasional loader use, and probably wouldn't go larger than a 4000 sized tractor if planning to use in the yard.
When buying, knowing what brands are supported by local dealers is helpful, as you may need parts along the way.
BTW...did a quick search on-line using your zip...I don't personally know much about the 1900 series of tractors, but I might consider researching further if in your shoes. I think they were some of the Shiburau (sp) mfg tractors from the 80's...and if i recall, my dealer has mentioned getting parts for some can be tough. Maybe someone else knows about these:
http://www.tractorhouse.com/listingsdetail/detail.aspx?OHID=6898299&