Good Advice here...
Except the clowns who reflexively post "SV650" to every "which bike should I get?" questions like they have some kind of motorcycling Tourette's syndrome.
-Any SV650 you find for under $2500 will be kind of clapped out (and you're not talking Canadian dollars are you, Ben?).
-The SV is great on the freeway but maybe not-so-good on dirt roads, especially if you want to "upgrade" from an XL250.
We here at MO recently rode a DR650, and we've ridden the Honda XR650L frequently as well. You can check this review out:
http://www.motorcycle.com/mo/mccompare/opendp.html.
Our latest review of the DR is pending. In any case, I think the DR, A Honda XR, or a DRZ-400 would be fine. However, I don't know what you mean by "well on the highway". Do you mean fast enough to keep up with out shaking you to bits? Or do you want wind protection and lots of comfort? For the latter, you need to forget about the more dirt-worthy DP bikes and think about a KLR650.
Anyway, whatever you choose be sure to check out this site :crazedlist.org. It lets you search every Craig's List Site all at once and should help you find a bike easier.
-Gabe