here's my .02 for what it's worth:
I also have problems with my feet going numb/falling asleep in both my road shoes and my mountain bike shoes. The main thing I'm noticed - if I lighten the load on my feet the numbness goes away. In other words - use my hip flexors, back muscles, stomache muscles etc etc when pedaling more than pushing with my feet. Before I spent any more money on shoes - my suggestion would be to pay closer attention to how you're pedalling and see if you're pushing with your feet - especially on the downstroke. If yes, try using other muscles on the downstroke and see if that doesn't help the foot problems.
As for walking in road shoes, I bought some clip covers to help make walking in them easier and to save the clips. It didn't bother me one way or t'other to walk in road shoes although that being said: I prefer to walk in my mountain bike shoes just because it doesn't change my gait.
Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body, but rather to skid in sideways, champagne in one hand, strawberries in the other, body thoroughly used up, totally worn out and screaming: "Yeah Baby! What a Ride!"