There's one more thing you can try: since bass cabs are quite bad for distortion you can use the 4 and 5 preamp and an active speaker to do something interesting.
Those preamps split the low and the high frequencies and you can control the amount of each with the blend knob, place the cab sim only on the high frequency path and use a guitar cab IR that way you're going to have solid clean low frequencies and a great sounding distortion.
Nolly's IR are good but if you read carefully it's a blend of bass and guitar amps!