Upgrading sub to get a live feel.

I currently have a set of JBL 4319 which has its history as 4310. They are studio monitors and as a result they sound like studio monitors you hear everything, but they lack the physical presence on the low end. They have wonderful mid range and voice presence. I also have a pair of SVS SB1000 to help with the low end. 

I want to eventually upgrade to JBL 4367 with upgraded pair of subs, for this reason, but in the mean time would a sub upgrade be considered before the speakers.