John's right on with 20 ton machines. Pound for pound they're the best value in the used market. I've been working on and around excavators/trackhoes for 25 years and I'm still surprised at their capabilities sometimes. There's times you think the machine you have is too small to do a particular thing and they handle it like nothing. That being said, Mini Xs can do a lot of work for as small as they are but they're pretty expensive for what you get. For what you're doing you're going to want a thumb. Hydraulic thumbs are nice but a welded on static thumb works great too. It's mostly minis that have rubber tracks. Some of the rubber tracks that don't have actual chains in them don't last that long and have to be replaced periodically. Some of the larger rubber tracks that have actual chains inside them with rubber molded on the outside last a long time though. But rubber still wears faster than steel. Stay away from any machine that has any exhaust after treatment, especially pre def stuff. My policy when buying a machine like this for myself is the older the better because an old machine will be cheaper to buy and parts will be cheaper, less electronic crap, you get my drift. If I'm buy a machine like this for myself I'm not looking for high production though. @John@Outfront, your JCB is considered a midsize or "midi".
@Dockmaster A 335 is a pretty big machine. Someplace in the 70-80k lb range. Probably a lot more machine and $$ than what you need.