Excellent point! bb4tb is right.

A bit more searching on AVSforum yielded a user who claims to get 'pretty flat' response out of the 1500 down to about 20Hz using a BFD parametric equalizer but there are no professional reviews to be found and no reliable reports of frequency response at measured levels.

Based on the comments of users on the net surrounding the PF-1500 and the subs in the 2004's, I am confident that either pair of LFM's will easily outperform what you have in place now.

Tony.