I dont think running copper tubes through a standard heatsink would net you much gain as you have to deal with the thickness of the base of the sink, the fins and the copper tubing thicknesses to contend with, and to get good contact you'd have to epoxy them in with arctic silver epoxy or something similar, at that point the air cooling of the sink would be near worthless...the waterblock with a heatsink seems like a good idea to me, even just as an emergency backup if the water system failed