Allright, once again I'll mention that I'm not the swiftest when it comes to transistor Sunns, but...
How do you figure
your amp is 500 watts? By what measuring criteria? Does it have additional output transistors and different power supply? Is it some sort of prototype?
500 watts through each of two cabs would require a
1000 watt amp, and even if your amp is indeed 500 watts @ 2 ohms, it would only be 275 or so @ 4ohms, or are you shooting for
each cab to be 4 ohms for a total 2 ohm load?
Finally, watts ain't that big a deal, a 500 watt amp is
maybe a couple dB louder than a 300 watt amp.
I know it's fun to talk/brag about watts, but if
loud is your goal watts is only a little piece of the big picture. The speakers are far more crucial to loud, if you want impressive stage volume double your
speakers.