Do you mean Garden tractor or Lawn tractor, the Deere 304 seems to be a lawn tractor i.e. no ground engaging attachments, a Husqvarna GTH27V52LS at about $500 less is listed as a Garden tractor.

In either case hitting tree roots, rocks, bamboo is probably not a great idea. As far as flat tires I guess if you drive over sharp objects, thorns etc, nothing is going to be bulletproof. I know we have some nasty thorns around here, every kid who rides their bike through a field gets a flat, perhaps replacement tires with a heavy tread would be an option if you have that sort of thing.

Really boils down to what you need, deck size, HP, 4 wheel steering or not and most important is there a dealer or service shop for the brand you choose nearby for when you need replacement parts. No matter what you get sooner or later something is going to break and need to be replaced.

With 3 acres to mow, I would go for the heavy duty models as you will be putting a lot of hours on them.

With your lot description, I would be inclined to look for decent used compact utility tractor with a rear mount or belly mount finish mower. They are out there. I personally have a gray market Iseki (Bolens, Massey and Cat Challenger series mfr) diesel w/ 19hp and a tiller. The tractor cost $3K with only 650-hrs on it and I did have to put maybe $500 more in parts to rebuild the top end of the motor (turns out didn't need all that, just some new rockers, but that's another story). They are out there, turf tires and all, and they will withstand the kind of abuse you allude to. Kubota makes good ones, and good used models are plentiful. 60" mower size is pretty standard on those.

How about an X324, X340 or X360? Any Toro you try is an MTD just like the Cub you had.

What you really need is a big compact and a brush hog :)

It sound like you got some coin, a x500 with a 54 inch deck will do it , and try going to as many DEERE dealers as possible work that price they will come down a bit.As far as hittin stuff that makes a new tractor old fast , shellin out that cash , you might want to get rid of a few obstacles.

3 acres with some inclines...automatically rules out x300 series John Deere. Since you said NEW tractor I suggest an x500 thats about $5k i think. I have a x304 and its great at mowing flat land an acre or less. I would never do what you want to do to my x304. My transaxle would overheat and die. And you cant change the fluid or filter on that x304 transaxle.

At my former property, I purchased a used Gravely to handle an acre of some of the roughest and inclined slope most would dare mow. It was amazing and bullet proof. I would recommend it to anyone with slope or difficult terrain.