Don't bother changing that crankset unless you want different gearing.

I was using an R600 and switched to a 6700-series 53/39. Both cranksets shift great, and I don't think I'd be able to tell them apart if it weren't for the different gear ratios.

If you're not going to change the ratios, or you'd stick with the same BB size (the Secteur has regular English threading, right?), keep using that R600 until the teeth wear down. It's a nice crank.