[daltore]

All, let me repeat, ALL major brushed DC motor controllers with the current supply you need use PWM. It's generally better than straight voltage control anyway, you get more torque and efficiency out of it, and it's just easier to produce. And there are a couple of ways to counteract issues with linearity. The Jaguars do it for you, although no one quite knows why yet (even my contact with Luminary Micro says they don't know why they're so much more linear than the Victors), but even if you used a Victor or a Thor, you could just square the the signal speed out to the motor controller to counteract the natural square root curve they have. Linearity really isn't your problem, the biggest attribute of a motor controller would probably be its frequency and resolution (higher the better). I'd suggest just looking at price and current capability, and once you've narrowed it down, look at reviews. As long as there isn't anything too outstanding in the customer reviews, it should be okay.