what about using the 2 outputs of your sansamp ?
the affected one into your 2pro input
the parallele one into your 4 pro input ?
I say go with this. You'll have the dry/wet tone and then when the overdrive isn't on, you'll have the two tones texture. In my opinion, nothing beats having 2+ bass tones going at once. The texture and how much it fulls up sonically is great.