In terms of phase cancellation it is very important that you constrain the bass to somewhere in the middle, a lot of PA systems are in mono, especially smaller ones.

The other point to remember is that the even if you want to play with the panning on your bass, it wont produce the sort of effect you would like. This is due to the properties of the human ear. Below a certain frequency (i forget which one, around 300hz maybe) our ears are less good at localisation, this means that although the sound might be coming from the left at 100hz our ears are not good at pin-pointing the direction.

Couple this with the fact that when printing on to vinyl the bass must be constrained as this will cause the needle to skip out of the groove.

There is also the fairly obvious fact that we (meaning I in this case) want as much bass power as possible from the system we are working on. Not to wash the system out, but to ensure that our bass is being reproduced effectively. Making sure that your bass is eminating from both speakers means we get more power!!!! mwahahahahah!

there is a free plugin called BassLane which can constrain the bass frequencies that can cause vinyl problems.

There is a technique whereby the upper harmonics are distorted on the basss line, this gives better definition to the tune of the bass without the producer having to raise to volume of the bass.

hope this helps