What would you replace the bearings with? Why are they loud?

A bit of a tangent, but related; If I get Elites or SLs, I'll need to buy a cassette to go with them. I currently ride Ultegra. Should I stick with Ultegra or move up to Dura Ace? Is it worth the difference? (Assuming it's okay to go Dura Ace on the cassette only) And should I consider a different sizing of gears on the cassette? My bike is outfitted as a compact and I live in Florida where I currently only use the big ring in the front and vary the back.