Remember that 'Behringer watts' are normally far less powerful than the same value in RMS or AES watts. At best it will be around 150W RMS, and you may find that the Peavey actually has a very similar power output compared to the Behringer. It may be worth bringing out the speaker connection (upstream of the crossover) from the Behringer and powering it from the Peavey and see how the amp outputs compare using the same speaker configuration. Or just try with the preamp out from the Peavey going into a line-in of the Behringer.