I would definitely recommend trying out both mid/side processing (which is already included in Alloy/Ozone - I can also recommend the Voxengo stuff, especially when for free ) and Izotope´s multiband when it comes to treating stereo mixes. The latter I have found to be particularly useful to really center the bass range by applying negative amounts of widening (yep, pull that slider all the way down and listen what happens). Since many bass sounds (esp. in the EDM/dance domain) have some sort of modulation going on, that´s useful for giving an extra oomph - and of course when it comes to cutting your stuff on vinyl (which you should ALWAYS leave to a professional mastering engineer by the way.)
Speaking of single/isolated signals S1 can be handy, although you can, as has been said before, really quickly mess up your phase alignments, so checking in mono is a MUST for club oriented music. You´ll hardly find a club having a true stereo PA.
And last but not least: give Logic´s Direction Mixer a chance. It has a nice little "Spread" slider that can work wonders sometimes...