In what regard is the bass active? Is there an active pickup with a volume and tone control, or is there a passive pickup with a preamp? Or both active pickups and a preamp?
Pot values for controls not related to preamp equalizers are determined by personal preference, but within a range that is appropriate to the impedance of the signal. Passive pickups usually get 250k or 500k pots, while signals buffered by preamps or active pickups generally get 25k, 50k or 100k pots.