I propose an alternative. The 5 band EQ is useful but it's a blunt instrument. It allows only some very coarse tone shaping.
I bypass the 5 band EQ in my Mark III and run a 31 band EQ in the effects loop instead.. It's such an incredibly precise and flexible tone shaping tool, once you get used to it and the tones you can craft with it, you'll never use anything else again.
I favor the Alesis DEQ series digital equalizers. DEQ-230 and DEQ-830D.
I use 31-band graphic EQ in my bass amp FX loops, but I use a 10-band parametric EQ in my Mark V FX loop, along with the 5-band GEQ. Parametric is so much more versatile and is especially useful for high gain guitar, where the frequencies that need to be cut are very specific, and narrow bandwidth cuts are ideal. I can cut all the different wonky mid frequencies with narrow bandwidths to get a scooped-ish tone without actually gouging out all the mids. And I can cut the harsh overtones in distortion (~2160Hz) with very narrow bandwidths, so it doesn't darken the whole high end.
The fixed bandwidths of graphic EQ are too wide, and cutting just one mid frequency can be enough to give it that hi-fi sound (which might sound good to play, but never works in a mix).
I got an Ashly 2-channel 7-band for the price of the 3-band Empress pedal. I run Out 1 -> In 2 to make it a 1-channel 14-band (10 fully parametric, 4 semi-parametric).
There's also the Source Audio EQ2. Pedal-size. 2-channel, 10 bands each. Gate, limiter. HPF/LPF & shelving options. It's digital, but it's very convenient to have 128 presets. It has to be connected to an app to access the parametric functionality, but once you save presets of your frequency and Q settings, you can adjust the gains from the pedal.
Parametric EQ is tone shaping with surgical precision. Graphic EQ is more like chopping at your tone with an axe.
Another great addition to the FX loop is the BBE Sonic Stomp, especially the new Pro version with the added 'Focus' (midrange) control. Tightens and sharpens the tone while keeping a thumpy low end. And the 'Focus' is a great mid-boost to make up for the mids cut with EQ. The EQ cuts and balances the mids, the Sonic Stomp brings that balanced midrange forward as a whole, while the 'Lo Contour' and 'Process' keep the highs & lows present and balanced with the mids.
