Get the biggest diesel, 4WD, hydro tractor you can afford and house. Also, buying a tractor specifically for one task may not be the best strategery. My SCUT has reduced my 'yard time' by more than half while getting twice as much work done.
With regular maintenance and not over-taxing the working limits of a tractor it will last forever, especially a Diesel engine which virtually eliminates the fuel storage problems inherent in gasoline. 10.5k for a Kubota SCUT is definitely within the ballpark. Used, category I 3-point PTO attachments are endless. A loader allasuden becomes everything from a wheelbarrow to a hoist.
IMO, a utility tractor really is an investment so give yourself a little reprise from the guilt of the up-front costs. Tractorbynet.com is an excellent resource for all things tractor. But beware, it's worse than heroin.
For example:
http://www.tractorbynet.com/features/used-compact-tractor-under-5000/