I've been using a Menatone PIG pedal for gain and overdrive for a few months now, and highly recommend it, with the caveat of me running it in a stereo set-up, so that I have clean lows with the PIG blended in. It's based on the Marshall 200, and has a very good grit and natural sounding drive, to all out distortion, but I feel it retains note definition well. I find often times with bass overdrive pedals the highs end up sounding fizzy, or like there is a fizzy fuzz overlaid on-top of the bass's actual sound, but with the Amp-In-A-Box style, I find it sounds less like an effect and more just like the bass through a pushed amp. Like the amp it's based on, it has a Master Gain, Bass Gain, and Treble Gain, plus a master volume. It's pretty good on its own, but using it blended with the clean, it really shines, and allows you to keep your lows well defined. I've also used the Maxon DS-830 in a similar capacity, and it's great too, plus it's easily modded to retain more lows.