What is the forums opinion of SVS subs?

They’re largely different designs. Yes, on paper SVS will deliver more deep bass per $ and sound quite good doing it properly set up, which is now much easier with their Pro series that includes integration software. Rel prefers to run off the speaker-level output and doesn’t offer integration software but by nature is easier to integrate without it. Bottom line, I’d take two sealed SVS SB1000 Pro subs at $1150 over one Rel sub because there’s a significant benefit to having two subs versus one if it comes to that. Past $1150, well, it’s all about budget. Don’t think you can go wrong with Rel, but then you start getting into Rhythmic, JL Labs, etc. territory that muddies the waters. Then it becomes a decision if using a speaker-level input or line-level input with integration shortware is preferable. Me? I’d read reviews of the various options and go with the one that offers the most of what you’re looking for. I don’t think you can go wrong with any of the above brands, but I will reiterate though that using at least two good subs is much better than using on great one. FWIW.

I do not have either, but both seem to be well respected.

One may also want to consider if integrating them into a system is easy or not.