I found a Metallic Green Volt tonight at my local PIAS. It is definitely more firm than the Copper Switches. Haven't thrown it yet, but it will hopefully stand out more than the Copper Switch. That thing is gorgeous, but just blends in with the mud around here too much on soggy courses.
Menacewarf - I'm with you on the stiff discs when it comes to everything but putters, where I've come to appreciate the softs for putting. For driving, I prefer the harder ones. I got a couple of those Innova G Star Leopards when they first came out and have experimented with the Pro and FLX plastics, and they just feel too wobbly in the hand. Grippy as hell, yeah, but just too mushy overall.
That being said, I've liked the slightly softer feel of the Neutron (Non-Copper) Switches I've thrown. That seems like a nice balance of grip and hardness IMHO.