Subwoofer to mate with Casta model C's.......

I have Casta Acoustic model C's with a 15" woofer, 17" custom horn midrange and 2" custom horn tweeter in each floorstanding speaker. The speakers are a sealed cabinet and are very efficient. My room now is 13 x 19 x 8 but soon will be 20 x 24 x 8 after renovations. I had previously owned an SVS PB13 ultra before purchasing the Castas but sold it knowing I wanted two in the larger room. The svs was a phenomenal performer. Can anyone give any recommendations on one or two subwoofers adequate to mate with the Castas and given room sizes. Budget is not an issue. THX in advance......
@Shiva, where can I find a Seaton dealer in U.S. or Canada?

@M-db, do you think running the subs speaker connectors to the speakers allows for better blending with the mains? In my case with the Casta C's the bass driver is very fast and acurate. I would need a subwoofer(s) that can achieve the lower octaves - 30-5hz with the same acuracy as the Casta's.
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05-06-15 Bacardi "@M-db, do you think running the subs speaker connectors to the speakers allows for better blending with the mains?"

I apologize, my statement is misleading. I used my Velodyne DD Plus' line level High Pass filtered output to accommodate the use of a much lower powered stereo amplifier while one of the mono-blocks was being serviced. This line level high pass method is usually tried when accommodating small satellite speakers to achieve a smoother response.

Are you considering the speaker/high level connectivity method used by REL? I found my short time with a Studio III and this method of connectivity limiting in some important areas. I was able to improve the subs performance somewhat by using an equalized line level signal from my then, DD-18.

Keep in mind my criticizing subwoofer performance with the staggering room variables that confront producing extra low frequency playback can be quite worthless. I do feel strongly regarding the value of ever improving subwoofer equalization and the ability to remotely control deep bass.

If your goal is large air then you might want to expand your search outside the Hi-Fi community to Danley Sound Labs and Meyer Sound. Good luck with your search.
I may look at the Danley subs if they have a scaled down horn that is wife friendly. If you could see the Casta C's in gloss brown grain you would be in awwwww....

I have looked at the latest Seaton submersible sub and it is very nice but the pricing is well over $3000 for dual 15's in one box. I think if the Danley's have something in that range I would be done and not need another. I don't think the JTR's look as nice as they have a commercial look to them(not my cup of tea or my wifes).
@Bob_reynolds, what do you think of the new Goldenear Supersub XXL? To me it looks like a great contender at $1999US. It would match the Castas well in the piano black but not available till late this year.