Hi Gmood,
Are you using Martin King's
Brines Acoustics FTA-2000 speakers or your own design? I've heard really great things about them.
When it comes to single-drivers, there is always a tradeoff - highs & lows for great mids, highs & mids for great lows, lows for great highs & mids. No driver does it all.
I suspect that Fostex offers a driver for each possible emphasis (and even more I haven't thought of). The 6.5" FE 168 Sigmas used in my Bens definetly trade bass punch for great mids/highs. They do 40Hz, but without punch, no matter how large the cabinet gets. Of course, I wouldn't expect a six incher to thump my chest.
The Hammer Dynamics Super-12 twelve inch driver trades high frequencies and absolute fine detail for great mids and lows. It has 40Hz punch when combined with it's 70 litre cabinet. The supertweeter is crossed in at 10kHz.
The Hammers have nowhere near the fine detail, articulation, or imaging of the C&C's, but do have terrific tonality. Far beyond their cost. Dynamics are a tough comparison. Once again, Fostex wins, but the Hamms are no slouch.
I just need to dial in some punch and I'm set for life.