This might interest you.
The P300 is rated for 300 watts. That means the power consumption of whatever components that you plug into it cannot exceed 300 watts (otherwise it shuts down). So you'll have to look up the power consumption (not output) specs on your amp and preamp to see. My gut feeling is that it won't work since the Parasound puts a fair amount of power and even if it did, I think the P300 would limit the dynamics of your amp.
Personally, I have used a P300 and found it to run hot and the fan was always running causing distraction when listening. I think you could do much better using a passive device rather than a power regenerator, especially considering your price range.