I was just about to post this same question...not that I'm hating my Dayton custom rig (t-amp + $25 bookshelfs and 80w sub), but I'm definitely looking for something with a bit more clarity and kick.
You would be downgrading if you got the Z-2300s. If you want more clarity and kick, you should just invest in a higher quality sub. The Z-2300 just goes BOOM BOOM BOOM.
the sub on the z-2300 goes booom booom booom becasue it's designed to fill in the frequency gap of those tiny little speakers.... if you get bigger bookshelf speakers they can play down to a lower frequency then if you get a sub you could set your crossover frequency at say, 125hz? and you would get more BUMP or KICK instead of WUBWUBWUB