Linkwitzriley 8 EQ Effect

http://en.wikipedia.org/wiki/Linkwitz%E2%80%93Riley_filter

This one should sound better at the crossover frequencies compared to the butterwoth 8. 
It has a constant phase shift = a non const, but linear goup delay.
It comes with a small amount of more CPU compared to butterworth 8 
Gain ramping is not yet implemented.

IMHO it is a candidate to entirely replace the butterworth.