bigger posts=better sound?

The diameter has nothing to do with sound quality..
The material is responsible for that....nickel, brass, siilver, gold etc. have different abilities for signal transfer.
in general, manufacturers rarely use something serious...most use junk like nickel or brass coated with gold to look good ... this is also a reason when you hear differences in cables...check out the quality of the connectors and you start to learn :-)

Interesting thanks for the input guys. While the diameter is higher the post is also drilled out so I’m not sold that the mass is changing things dramatically in this case. Archguy, I think you may be on to something with the contact area, it is greatly increased on both the banana clip side and the inside. These are viborg with a blend of copper and brass, as I understand it all copper would be rather hard to torque, Which it seems is also key... not planning on going hard for any new connectors but I’ll probably do the other speakers as that explains the difference I’m hearing!

Mass aside, my investigations have taught me that contact area is important.  This is very much a function of the connectors you use as well as the configuration of the binding posts themselves.  It's why I prefer spades. 

^ +1. Take a look at the Cardas CPBP post, or the even lower mass (and like the CPBP, machined from copper) Electra Cable Tube Connectors, available from GR Research.

Actually, a lot of people who know about such things believe that lower mass is better than higher for binding posts, and more important is the material it is made of. Gold plated means about nothing, but having solid copper for instance is more conductive than the more common brass.