I'd stand pat with the Suburban as-is.
Unless you are commuting a high number of miles every day, I don't think there'll be any 'economy' in swapping one used SUV for another. Better the devil you know. Consider too that right now, these years, the parts are widely and cheaply available. Can the same be said for parts for the other vehicles you are considering?* There is also no such thing as 'too much' room. A Suburban is no larger than a full sized standard cab longbed pickup. It will go down any 'forestry dept' -maintained road. Jeep trails? maybe, maybe not. You want ot go crawl around in tight technical crap like that, get a Jeep. Or a Suzuki Samurai. They can be had cheap and your Sub can readily tow a toy like that on an outing. But if as you say money will be very tight, you aren't going on a lot of trips nor can afford to go break or damage something on a tight trail, anyway. Be consistent and thorough in your reasonings.
* just today I replaced my Suburban's radiator, water pump, thermostat, upper and lower hoses, for under $300 in parts (via rockauto). What would that cost on an Xterra?