Gary,
Glad you like some of my ideas. My understanding of the PSE (Porsche Sport Exhaust) is that it has cut out valves just like you're planning to install. The only difference is that theirs are vacuum controlled rather than electric. Exactly how the PSE valves are controlled though I do not know. I think there's some kind of electronic wizardry that they use in the control. The PSE does bypass the muffler when engaged.
The intake on an engine though has vacuum. As the pistons move down the intake valves open and the pistons suck in fresh air and gasoline. Theoretically I don't think you need a lot of electronic wizardry with vacuum controlled valves then. Just hook them up to your intake vacuum and they'll open more as you increase revs and thus give you more sound and maybe more power...
My gut feel too is that vacuum valves are more robust than electric ones. The wastegate on a turbo is basically the same as a vacuum valve, except it works off of boost pressure. They are made to withstand very high exhaust temperatures.
Since you've got a turbo car you really might want to give sharkwerks a call and see if they can hook you up with a couple of their valves.
http://www.sharkwerks.com/products.php?pid=153
They gave me the name of the company that makes their valves, but I don't have it at home right now. This company that makes the valves though had a turbo boost pressure controlled bypass valve (like a wastegate valve). That might be just the ticket for you!
Imagine that - just run a hose from the boost side of your turbos to the bypass valves. As you get more boost pressure, then you use a little bit of that pressure to push the valves open.