You may be able to remove a reducer wedge and fit a straight 1.5in steerer in your existing headset. But if your budget is lower anyway that's no use I suppose.
Domains are good, there have been a couple of threads about them on here recently.
I've not been to Whistler (I'm sorry to say), but if the trails are smooth-ish then the Domain should cope fine. It's only on rocks and bad braking bumps that my old one showed itself up a bit.
Forgive the plug, but I have a new 2010 Domain 302 that I took off my new bike for sale cheap, tapered steerer – with headset – in case that's of interest. Email in profile.