Ok, a couple of questions about combo amps and their impedance. Which is the better choice as far as going with 4 ohms or 8 ohms when using both active and passive eq on a bass? For example, I have an Ibanez BTB 400QTM with 18 volt active eq, a Washburn and Fender P-bass (both with passive eq). How does the impedance effect the overall tonal qualities if any? Any help is appreciated.