Botman, I did not realize the Axis 12" drivers were on sale at PE. In that case, you can consider this OR the Sound Splinter RL-S 12". The RL-S will have a little bit less total output/SPL potential but greater over-all motor linearity at extreme excursion. The AXIS will have more output potential at the expense of some linearity at extreme excursion. Both are world class, and superior to just bout anything else at any cost.
TC Sounds/Audio Pulse designed the LMS Ultra(the motor used on the RL-S) to have ultimate SQ with extreme SPL capability, but oriented a little more towards SQ. The AXIS was designed to have immense SPL while retaining 'most' of the SQ, but a little more oriented for maximum SPL. In the end, it would be a wash at moderate to medium high SPL - with both having identical SQ. It's at the extreme end/level of SPL that they two will have some differentiation.
$400 w/free shipping will make the AXIS around $100 cheaper than the 12" RL-S each. It would be a hard decision for me. It would come down to modeling both drivers and deciding which one has better performance in the size / type cabinet you want to use.
-Chris