How much does the transport affect sound quality?

The transport makes a big difference. I can't comment on the Cambridge because I've never heard it.

As far as telling you what kind of differences you'll notice, I really can't. Its no different than matching any other component. Different transports will sound different from each other.

There is one thing, though. Sometimes its beneficial to use the same brand for your transport and dac. If the same designer made both pieces, they're usually meant to work together. Some even take it a step further and use proprietary designs. Wadia, for example, has a feature they call clock link. But to take advantage of it, both pieces need to be Wadia.