I just modded the R25. I added a 18k resistor to the 33k resistor. Gives it a touch more high mids, and mellows out the lows and low mids. This helps with lower tuned baritone guitars like mine since before the mod it was kinda flubby sounding.
I've since traded it but I honestly can't remeber what I changed haha. This was recorded with 25w Blackback speakers though so that's also a big factor.