Thank you everyone for the quick and thoughtful responses. Some of the other techniques we've tried with the barking, to wit: ignore, leave the room, re-direction, pivoting, hand clap, verbal stop cues, book drop/loud noise, shake can filled with coins, etc. I've also tried occupying him with toy after toy, bone after bone, but he gets bored very fast. he is a very high-drive dog. I keep a floor cord on him to pivot him when the barking begins. I take him on 4-mile runs with little fatigue setting in. Or I take him on daily bike rides of 1.5-2 miles at fairly high speed. I have a very active lifestyle and he loves to participate. But trutfully, it's not enough to wipe him out.
I have been reading extensively, and spent money on individual lessons that tell me he is not physically tired enough and not mentally stimulated enough. Oh I should mention I also did a six week agility training course with him. But there's only so much time in a day where I work full time and when I get home, he barks because he is so stimulated (with excitement). It's hard to bring him down a notch.
I was thinking of the collar to help in the evenings when my wife and I try to relax. and I don't mean watch 6 hours of tv. This happens during dinner and discussion, when guest come over. It's really bad. I have no desire to give him up but this is my last resort. The collar, I am thinking, would be used only during the evenings. My neighbors have told me he is quiet during the day (he stays and sleeps in the kitchen) but when people are around, this switch goes on and his excitement skyrockets.
I would never use this at day care or in a kennel setting. It's for home use only. The funny thing is he does not bark in the car, nor on walks. It's strange.
That's really all I can think of. I appreciate people's response, and would love to hear more.