Power supply woes?

I built another little preamp today (this time just a CE followed by a CC rather than the shunt thing I used before), just to see if additional drive was the issue.  Did not seem to help.

However, it occurred to me that it might be the power source I'm using.  I've been using alkaline AA batteries.  But calculating things out, for 12v to produce 5 watts, the batteries would need to be delivering around half an amp (not counting what is dissipated in the transistors).  I always assumed that the batteries could deliver more amperage for a shorter time (the amp-hour rating).  However, I forgot that that batteries have voltage curves.  I measured the voltage output when the amp was running, and it was closer to 9V.  So, I think I need to go find a better battery to use :)

(I actually tried a wall wart, but I think I was either getting feedback into it or it was just noisy, was getting a weird output when I tried to bring the power above what I had with the batteries.)