Best frequency for spl

Im just wondering what your guys opinion is on the optimum frequency to tune a ported encloser for strait SPL compition. My box, as it sits, is tuned quite low. I did good in comps last year but am always looking for ways to improve. Any thoughts would be apreciated. Before you ask my gear is as follows

4-12 Pioneer 305DVC

Alpine Head Unit (cant remember model number right now)

Audio Control 3.1 Pre-amp

Pioneer Rev 61/2s in kick pods

Orion HCCA 425 to the subs

2-MTX RT-01 crossovers

1faurd Stinger Cap

8.8 cubic ft ported box tuned to 26.6 hz (Chambered)

Rockford 2002 to the front speakers

I would attack this from a different angle first. No offence intended, this is the course to improving sq and SPL. I would eliminate the Alpine cd player and the 3.1 and both MTX crossovers and replace with a Eclipse CD8443 (or new CD8454) or CD8053 + balanced line driver. One of these cd players will drastically improve your sq (a side benefit) but drastically improve the performance and capabilities of your system in the SPL quest. The more times a signal is manipulated, the more loss of signal there is. This one cd player will do all the work that is being done right now by the 4 units that you have right now and much more at the same time. The equipment that you have is great, don't get me wrong, but streamlining the system and understanding what needs to be done is where to start. In this case I would start at the beginning.

Should you say "ROb you jerk, that is not what I wanted to either know or hear" I would recalibrate you box much closer to the loudest resonant frequency of the vehicle. This is usually up around 70hz. It will be a ported enclosure obviously and be a "one note wonder" that will play much louder than what you have right now. The tradeoff will be loss of usable and listenable sound and lack of bottom end depth extension. Read again what I posted and see which path you want to attack first. My bet is the sub box as it is the quickest and cheapest route to your SPL quest, then you may want to attack the recommendations that I made above. If you have questions or comments on that I'll be glad to answer them for you.