Ok -my musical tastes are very different - I listen to punk and old new wave, mainly.. but I'll give this one a shot...
I upgraded from a pair of JBL's to M40's. The JBL's were a 2-way with a 1/2" titanium tweeter and 8" woofer. I was blown away IMMEDIATELY by the detail of the new speakers - and it seemed like I could hear MORE bass from these!
After listening to the M40's exclusively for a while, I hooked the JBL's back up... I found that they were definitely louder, had very tinny sounding highs, and very lacking mids (just missing).
Now for the bass - the JBL produced much more bass VOLUME, but the detail just wasn't there. The Axiom just let me hear more bass detail - actually heard the notes! I think that these coupled with a subwoofer would easily blow the JBL's out of the water.
I would say even a cheap subwoofer and M40's would be better than the JBL's - the sub would get some more bass volume for hip-hop, but the M40s would provide detail that the JBL's probably could not provide - which could be really great for some kinds of hip-hop, and possibly matter less for others. I think you'd like the smoother sound of the M40s for movies as well.
It might be more money, but not TOO much more - and I think it's money well spent, especially if you think you will have the upgrade bug. With the M40's, you can scratch that itch with a good sub...
