Whatever works for you, you could have them in front of the MP1 or in the MP1 loop, in the loop lets you switch them in/out in the MP1 patch, in front you'd have to stomp them on/off. Every gadget you put in the signal chain will add noise, affect (reduce) the dynamic range and also you need to get the gain structure right. My preference is keep it all simple and make the sounds with my fingers, also I'm not chasing a particularly "processed" sound. IIRC Aphex started life as an aural exciter designed to make vocals stand out in a mix (as they add lots of upper harmonics). I don't know much about the BBB maximizer stuff but other members here use them I think
. Basically you need to try it and see/hear if it enhances your tone to your taste. Although my advice would be get your tone(s) sorted first (at stage volume), then add things in one by one and compare.