BI AMPING

MikeL makes some great points. I use two EVC ultimate attenuators in my biamp setup.

But I think in this case it really makes sense to go for the active x-over since you really do want to filter out the bass freqs going to the 300b SET amp for the tweets since your available power is fairly limited.

That should increase your dynamic range allowing for higher max SPL.

If going for the active bi-amping the thing you need to keep in mind is the woofer x-over freq and the slopes of the high/low pass filters of the speaker's built-in x-over. What type of speakers are you planning to biamp?