What DSLR to upgrade to?

I shoot with both Canon and Nikon DSLRs and currently at the moment I have the Nikon D5000 and I'm looking to upgrade in the late summer, out of the four I have chosen which one is ideal for me.

I take pictures of moving subjects, so I'm looking for something with faster continuous speed and great image quality.

Canon 600D
Canon 60D
Nikon D5100 or the
Nikon D7000

Regards
Lorenzo

Added (1). Nikon D5000 with 18-105 VR lens, if upgrading lenses is more ideal than DSLRs then would a high quality lens be more appropriate than the one that I've already got.

You don't need to upgrade your camera, spend the money on better quality lenses to use with what you already have.

Some of the best images I've ever taken were shot with a Canon 300D, with the Canon 100-400 L series lens on the front of it.

Better would be to invest more in lenses. You don't get great shots by holding down the trigger. You get great shots by waiting and selectively shooting.

switching over to canon is a dumb idea since you already have a Nikon system.

Get more lenses. What lenses do you have? What is your budget?

I'm with the others. Even considering Canon is pretty stupid as you'd have to replace your existing lenses and flash as well.

The D5100 is the direct replacement for yours, but unless you're having severe problems with the camera, there are far better uses for your money.