Mike,
I have a '12 5083E and I will say this. For my original intended uses, that tractor excels at. I have a 563 loader and It will pick the rear tires off the ground if I dont have the counter weight on it. Moving round and square bales with it (kuhns system) it smokes my father in law's older ford. Grantedmine is only about 30 years newer lol. Now the other hand, if you think your going with a disc bine for hay, get more horsepower. I haven't seriously looked into them, but 69 pto hp doesn't give you to many options for running a power sucking disc bine. I have dabbled into some light farming and I dont have enough grunt for the real work. Trying to pull a 16' disc is doable, but I can't cruise at the speed I need to, and I have to constantly bump the disc to keep form burying the tractor. My suggestion would be to step up to the 5101E if at all possible, That should keep the price down a little bit but it will make that disc bine pull so much easier and give you more options.
The air seat is a needed upgrade and I highly reccomend that. I didn't do it and I have found the floor of the tractor a couple times. I would also suggest adding the third function to the loader. Currently, I tried to run the cheap route by using the rear remote and running hydraulic lines to the loader, while it works, its definately not the best option. Along those lines, Id suggest the 3rd or 4th remote is possible on the rear. The newer attachments take advantage of these and make life alot easier if you can afford it.
I'm not knocking the model at all, but if you are planning on doing real farm work and not heavy duty compact tractor work, your gonna need the horsepower. If you can't afford the upgrades, you just have to find more creative solutions to get things done. hope that helps.