Upgrading power cord.. proven upgrade? or crap?

Completely agree with stringreen. Powercords are more noticeable than interconnect or speaker cable. They make profound differences too, but the powercords are HUGE. Try one of the dozen from Purist Audio Design. Extremely effective.

The right way to do lightning and surge protection is with a surge arrestor at your power service panel.  Home Depot has panel-mounted arrestors for ~$60, and external (if you don't have room in the box) for ~$110.  Protects every electronic device in your home, including the stereo.  
analoglvr: you are allowing your bias against AC cables to miss out on this huge facet of improving your audio experience.  I've heard plenty of bad AC cables, but if you hear a good one, such as a Purist Audio Design, and listen, I'd be surprised if you didn't enjoy the improvement in everything.