I don't have the amp yet. So calibration and everything else comes later. The rough design I put together in WinISD doesn't really show what the end result is going to be.
Here's set of graphs:
The blue line indicates how each of the subs should perform, before EQ boost, with 600W to each driver. All based on very loose estimates of 5ft^3 internal volume, which results in a Fb of 41.42Hz and Q of 0.713. A 3rd-order Butterworth highpass filter is included at 5Hz to account for electronics drop off.
The yellow line is the same enclosure, but with a Linkwitz Transform (approximated by the DCX2496, hopefully) applied. This isn't necessarily the anechoic response I am going to end up with, since I'm going to apply whatever filters are necessary to get flat in-room response to as close to 5Hz as possible.
The drivers can each take 1000W peak, and in fact they aren't being driven to their xmax in the yellow line graph. I don't know what the EP2500 peak output is. Couldn't find it anywhere. But you can add ~2dB to the SPL graph if each driver gets 1000W instead of 600W. And these graphs are for one sub, not two.
If the Linkwitz Transform doesn't need to have an F3 as low, with room gain, then the SPL also goes higher. For example, switching to an F3 of 18Hz moves the 600W SPL from 102dB to around 108dB.
Basically, that's why I'm saying the models aren't worth a whole lot right now other than to serve as basic validation for the design. Because the actual result is going to depend entirely on what filters I apply to get flat in-room response.