I've owned 6 SVS subs (that I can remember). I've had no issues with any of them, including some that were fairly old when I purchased them. I ran a pair of PB 12 Plus/2 subs for quite a while, but eventually went to all sealed subs. Rythmik is another great option as is Power Sound Audio.
My main system includes 2 SVS SB 13 Ultra and 2 Rythmik F 25. I haven't owned any Rel subs, but have heard them. My subs are well integrated with my mains and only make themselves known when the source material calls for it. I'm sure it would be nice to have 4 high output Rel subs, but I can't justify the cost difference and doubt that it would sound much (if any) better than my current setup.
My main system includes 2 SVS SB 13 Ultra and 2 Rythmik F 25. I haven't owned any Rel subs, but have heard them. My subs are well integrated with my mains and only make themselves known when the source material calls for it. I'm sure it would be nice to have 4 high output Rel subs, but I can't justify the cost difference and doubt that it would sound much (if any) better than my current setup.