My favorite for my 76 precascaded Marshall JMP is clearly the Rodenberg 728NG
I tried
Suhr Kokoboost (very clean, best neutral! cleanish boost, the mid adjust is cool, but not quite in the region I like, "lacks" the stability ((ok as it is not intended)) of a tubescreamer clone)
MXR CAE 402 (ok, but not as good as the Kokoboost, degrades the sound more, overdrive pedal side is too brittle/grittle, less gain than the koko)
MXR Micro Amp: nothing to write about, more aggressive than its bigger brother, but not as clear)
Analogman King of Tone 4 (quite open (for a tubescreamer, my choice if I had no rodenberg, more neutral playing feel, little more tubescreamer gene, stays quite clear even with much gain, quite interesting/solid, if you will use a strat neck pu, very! transparent)
Xotic RC Boost (more harsh and little sounding than the Analogman KOT, but ok, bass gets too muddy when added, with more gain a little muddy)
Maxon SD9 (to much mid hump, little dynamics, but ok, dominates the amp, muddy)
Okko Twin Sonic (quite a lot headroom, not bad, but gets muddy with higher gain settings, a little brittle like the RC Boost, not much gain, a quite neutral sounding unit)
Boss DS1 Japanese: (very! little ((the least)) midrange, quite spongy feel, gets too muddy, little dynamics
Blackstar HT Boost: (boring, nothing special, the tube does nothing)
The Rodenberg 728NG (probably not much known in the US is a booster with overdrive which I prefer to the Kokoboost which adds certain frequencies I really like, it enhances/excites the sound, but does not color the amp in a non transparent way (probably like the Keeler pull or klon (booster side 707), I do only know sound file comparisons of the klon/keeler, will try Keeler Pull soon).
The overdrive side 808/909 is a little more tubescreamer which I prefer to the KOT, as it is a little more open and not as neutral playing wise, you can adjust bass cut or not, the pedal is highly con-figural, try it, exceptional pedal for enhancing your amp, quite a lot gain is available (like Vais Eat em and Smile Solo Sound.
Will try the OCD and 101 Lehan Lab Dynamic D and Keeler Pull next week
https://www.youtube.com/watch?v=vOR1fyOs05c
I do not like normal tubescreamers, as they are too boxy (non-dynamic) in front of (this) marshall...
right now, my ranking for the JMP Marshall with a Rosewood Strat with vintage sc and alnico humbucker on the bridge:
1. Rodenberg 728NG
2. Analogman KOT 4
3. Suhr Kokoboost
Greetings
Kai