Yeah, that chart was a real pita, without the under scores the formatting was a complete mess
One last piece of advice, with sealed subs when you move to a larger driver, everything being equal you need a proportionately larger box to get the same extension.
You can see below how this works. All 3 subs we're given 100 watts.
The larger sealed 15" subwoofer shown in orange will have more output than the sealed 12" subwoofer shown in yellow, but it needs a larger box to do so. The frequency response curves however are the same because of the ratio of the driver size in relation to the box size.
The ported 10" shown in blue can hold a flatter response to it's tune while also having more output around the tuning frequency in around the same size enclosure as the sealed 12".
This isn't meant to be a perfect example of your situation because the Xs15, Lv-12r, and pb-1000 all use different drivers and amplifiers.
Some drivers will do better in smaller boxes, but the info provided by Jim, and the frequency response info provided by Basshead suggests the xs15 is reliant on room gain in at least the mid 20hz area and below to achieve a relatively flat response.
Room gain can help significantly to boost the lower frequencies, flattening out the curve, but it is dependent upon the size of the room.
So yes the Xs15 is definitely the more powerful sub, it has 500 watts available compared to the 300 of the pb-1000 and lv-12r, and it likely has the highest excursion driver.
However if you find out later on that your room only boosts up to around 20hz (just an example) and you try to equalize the XS-15 to even out the curve, that extra 200 watts (or 2-3 decibels available for equalization) will run dry, likely before you get close to the excursion of the driver and might still not be enough for a flat response with more output than the other subs.
So basically the box size and type are equally important as the size of the driver used.
It seems to me your situation would call for either a sealed sub with enough Eq to reach the frequency you want with a relatively flat curve, or a ported box with a suitable tune. You will pay more for the eq'd compact sealed sub, compared to the ported sub with similar performance.