For the price of one of these 10" RSL subs you could get a pair of 15" Dayton SUB-1500 subs if you have the space for them.
I found a chart which includes CEA 2010 measurements of the SUB-1500 as well as a few others. The Dayton wins for total output and dB per $, but the RSL wins for dB per cubic inch and for WAF. For $100 more than the RSL, an RBH I-12 would be worth considering, offering an attractive enclosure with a smaller footprint than the 15" Dayton.
Measurements for the RBH claim greater output than the Dayton, although no indication is given whether those are at 1m or at 2m. It's most likely an apples-to-oranges comparison.
Of course, none of this offers any indication how any of the aforementioned units handles impulse response graphs / waterfall plots / spectrographs -- whether any of them will play with a ringing resonance or with control. If the SUB-1500 bears any resemblance to
its little brother (the SUB-1200), it ought to be very well-behaved (somewhat in contrast to the SVS PB1000 that BSA recommended).