I'd have to agree with John. SVS makes an awesome sub but I've only heard one of their cylinder units and my Ultra. I am well pleased with them but they are above what you linked to in quality and output.
If money is not an object there are some very good and very expensive solutions out there.
I think a little more information from you could be helpful here. What are you lokking for specifically and what is your budget.
If you have the ability and room to do it a custom sub could give the best results. I have been fascinated of late with the IB (infinite baffle) projects. Do a web search on them if interested.