I can't decide on the placement of my preamp? My pedalboard is Tuner>Wah>Delay>Tremelo>Dirty Amp. I'm wanting it somewhere towards the front but am having trouble discerning if it is better before or after the wah. I also sometimes have a Rotovibe right after my wah when I want more colorful sounds. The preamp I have is the MXR Echoplex Preamp.