Energy C5 or C500

Yes, I saw those 500's at AA, the used 5's are $350 and no shipping cause a reord store in town has em.
I know that isn't a good enough discount for used, if they are basically equal speakers.
I read a few posts that said the 5's were a better speaker and the 500's were lighter and cheaper....cheaper in price compared when new.
Anyone know both of these and have advice to give?
Thanks for your input Johnny.

The 500s are not significantly lighter. Here are the specs for the C-5. They weigh 47 lbs. each. Here are the specs for the C-500. They weigh 44.1 lbs. each. Just the use of a lighter, more efficient magnet could account for the difference and would signify an improvement. Also, a more sophisticated form of internal damping could account for lower weight. Other dimensions are usually within an inch of the old model. The old C-5 used injection-molded polypropylene mid/woofers. The new model uses composite Fiberglas cones, which is probably a step up. Mirage's (same parent company) flagship speaker ($7500/pr OMD-28) is using a form of Fiberglas for its woofer cones as well.

Every time anything changes models, there's always a chorus to whine that the old model was better. It's not necessarily so. In my experience with the later generation API speakers, they have a faster, more articulate bass with more dynamics than the previous models did.

Thanks for all the info. You've been a big help!