I currently have a pair of Fostex FE126-based horn speakers and a SET tube amp that I built several years ago. Sound is really good but I'm finding I'd like to have fuller range (particularly bass). I'm trying to figure out if I should augment my system with a nice subwoofer and perhaps super tweeters, or if I should look at a high efficiency multi-way system (the 4PI system in particular has caught my eye). My music tastes vary - everything from hard rock to bluegrass. I don't play at super loud volumes typically. I will keep the full range speakers around regardless, but trying to figure out if it would be easier and yield overall better sound to add to my system or if I will have trouble integrating the sub/tweeters and a multi-way or different full range system would be the way to go. Any thoughts as to advantages one way or the other?