If your choice is XTZ, then go for the EDGE version as the ICE amp used in the EDGE version is known to be more reliable than the amp in the regular XTZ. But you will have to pay a premium of around Rs.10,000 for the Edge amp over the regular amp.
One more point to note about the XTZ is, these subs wont play below 19hz. I believe that its Infrasonic Filter is set to 19hz and hence it cant play anything below that.
The sound quality is very good for both movies and music. But I believe the SVS PB series will be much stronger than the XTZ around 20hz, while the XTZ will have its advantage above 30hz.
The XTZ integrates very well with the Main speakers for music. If you set this subwoofer properly, this subwoofer will disappear completely. This sub is also tight and clean. You will never get ear fatigue or headache even if you listen to this subwoofer for a long time.
If your preference is Movies, then go for the SVS and if you prefer Music then I will recommend to choose the XTZ.
IMHO the XTZ 12.17 Edge is more powerful than dual XTZ 10.17 (non Edge) version.
Rythmik is another option, but I have no Knowledge about them expect having read rave reviews about them online.