I was once "dying" for a tractor with a backhoe on it. Bugged the wife to no end...finally she said "shut up...my brother is selling something, go buy it"
I ended up with an industrial JCB backhoe/loader (15 1/2' digging depth)
Paid about 13K for it as I recall.
At the time, I was pricing new subframes for a Kubota and (very poor) memory tells me they were around 9,000 new?
With today's economy, you might look at an older industrial backhoe/loader. Bigger, badder, stronger, heavier, easy to lift your house off your foundation with a pull of the stick...
Then, keep your tractor configured as it is.
Today in hindsight, I'm very glad I went this road. Loader/backhoe is far more capable of doing what I would have wanted a tractor/backhoe to do.
Just trying to throw some off the wall thoughts out there for you.
You could buy a used one, use it for several years and resell it for probably similar dollars that you paid for it.