MrSmith, what kind of music do you listen to? When you say your setup is crowded, I take it the room is small. That's good, because you'll potentially need less speaker to fill up a small space.
Many bookshelf speakers are able to ouput frequencies down to 45Hz, so unless you're needing the bottom most octaves you'll be best off putting your full budget on REALLY good bookshelf speakers and skipping the sub.
Either way, I'd stay far away from towers at that price.