I have several thoughts, for whatever they may be worth. First, if you can get a better sub than the ones you have now, that would be great. But, your Klipsch subs are ported and the Paradigm is sealed, so the Paradigm subwoofer will actually not produce as much low-frequency output as your two Klipsch subs. There is a pretty good description of the difference between ported and sealed subs in Section VIII of the Guide, linked below.
Second, if you like what your Klipsch subwoofers are doing for you and you just want more of it, I would look for a way to get that in a ported sub. If you buy a better ported sub, with a somewhat similar tuning point, say no more than about 3 or 4Hz lower than the RW-12D's, you may be able to integrate all three into your system. Something that occurred to me, before I looked up the Paradigm sub, was that you could run the most powerful subwoofer on the front wall, and the two less powerful Klipsch subs on the side walls. But, they would all need to be ported (or sealed) in order to prevent cancellation from occurring. And, as noted above, the port tunes can't be too far apart.
Something else I thought of from your post is that, if you like the immediacy and "kick" of having a sub on the side wall, but you don't like the localization which results, why not make the sub up front play a little louder than the nearfield sub? That might give you the best of both worlds, and it also aligns with the idea of a more powerful sub up front with subs on both side walls. That should also increase the immediacy of the bass sounds and sensations without corresponding localization.
Alternatively, of course, you could just dispose of the two Klipsch subs and buy the best ported sub you can afford. But, in a room that size, and especially where you are already used to the sound and tactile feel of ported subs, I would probably stay with ported.
Oh, and yes, I do have the nearer sub a few db lower than the front as I noticed that helped.
I hope that some of this helps!