As said KTM would be choice,autolube if possible.
If you're budgeting stay away from premium bikes such as the CRM because they have attained a cult status they fetch a premium,I've had one and without getting bleary-eyed IMHO I felt a bit let down by the hype and raised value.
WR250=WOW amazing but usually caned and needing work,I loved mine but thought it was a bit too old and the draw of the Orange was too great.
2 KTM 200 exc's trailed and enduroed,fabulous,light,flickable,easy maintenance and part supply(Leisure Trail),they need a crankweight to benefit from "roll on" if your an old 2/t hand.Also they retain their value to the extent that I got my original purchase price back both times...be quick if you buy one they don't stay advertised for long.
Of course there are plenty of others to choose from,if you are solely trailing then you have a plethora of choice.I have had many 2/t trailies and crossers,any opinions are my own based on my experiences with no intent to offend anyone.