Hey, Doug.
If you're going to spring for a new unit, you might as well bite the bullet and get it with all the bells and whistles now. It'll be easier going into the purchase (and probably cheaper in the long run) than having to go back after the fact to try and refit with stuff you find that you really need/want. Comfort accessories are not really a luxury as far as a working mower goes. They'll save you a lot of time and wear & tear on you and your tractor. That kind of comfort & convenience is up-front money well spent, IMHO.
I bought mine used, but I honestly wouldn't mind re-fitting my 721D with the GH 25cu.ft. hopper/collection unit. Don't know if a tractor as old as mine will work with a new unit, but I think I'll do some research and find out. Watching the company's videos I would much rather back up to the edge of my woods and hit a lever and dump an entire hopper full of grass & leaves than have to get off the machine and lift out a bunch of full bags repeatedly. Either way, it sure beats having to rake up all the grass you've just mowed (or leaves you just mulched)!
Good luck with your purchase, and be sure to post some pics of your new 'Hopper once you get it!