I hate Sonar, but that's just me.
I use my Traveler with Cubase SE on my Powerbook, and mix in Nuendo 1.62 on my XP machine (the Traveler does the D/A)
I've always been a fan of Steinberg products, so I would recommend them on an XP platform over anything else. There are lots of good choices out there - it really depends on what you're going to use it for and how much you want to spend.
Dirk