OK, These are probably going to be some really dumb questions...

What is the advantage of shooting in aRGB if you end up in sRGB on your final picture?
Same question with setting the camera to IIa(adobeRGB) vs Ia or IIIa for a higher gamut?
If PS is just going to convert/dumb them down.
Aren't you taking a chance with that conversion? By chance, I mean you have no control over the conversion.

Wouldn't it be better to set the camera to the final output and learn to work within that color space?

I've ordered a Spyders3pro monitor calibrator. I hope I can perform a few experiments to test the PS conversion and my camera setting.