Going to a 4 gang box, the only real difference between that and other options is outlet and connections quality. So you are right, the effect of the 3 plug cannot be so bad. None of this stuff is really bad in and of itself. Its only when compared to something better that you notice.
If you use high quality outlets like Synergistic Blue that right there will probably be as good as some power conditioners. But even if you use the cheapest hardware store outlets there really should be no loss just from adding a few outlets. Use ones with screw terminals and use them for a better connection than the one where you just stick the end of the wire in.
