There are quite a lot of Big Muff pedals out there now: how do I know which one I want?

Well, apart form the obvious and slightly unhelpful answer of 'visit us and try them all out' (which you can definitely do!) we would suggest dodging the Metal Muff pedals since they are actually high gain distortions and not Muffs at all apart from in name. Instead, we'd share that the Tone Wicker model is super useful as it is the classic Muff sound with the handy ability to stay in a mix/band setup easier since it has a good mid kick in it. We'd say that the Deluxe Big Muff will give oyu pretty much every variation of that famous fuzz sound. And finally, to get to the point: which one do we actually like the best? Easy. The Op-amp model.

Should I put my EHX Big Muff before or after my overdrive on my pedal board?

Good question: in our experience, adding an overdrive to a Big Muff sound is pretty ineffective so we'd suggest having the overdrive first.

Which Electro Harmonix pedal is a recreation of the Klon Centaur?

The pedal you are looking for is the Electro Harmonix Soul Food. Is it worth a shot? Definitely.

Do I need a special MIDI pickup in order to use the '9' keyboard emulation pedals like the Mel 9?

No, you don't need any extra equipment or speical pickups of any sort. Simply plug into the pedal as you would with any other pedal and experience some amazing results!