Will this be active DSP? I'd suggest going with lower extension too. You can still have good sensitivity especially with two.
For your usage, I'd probably go with the B&C 15NBX100, the BMS 15N630, or the 18Sound 15ND530. These all have demodulating rings and good response curves. I don't know about prices which can vary significantly in the EU vs the US.
One other option which I think is pretty cool would be to use side by side 10" or 12" woofers for a total of 4 woofers. It will actually hold directivity a bit lower than a single 15" and will give more headroom without adding any height and still staying within the confines of the SEOS-24 width.