SVS vs REL and experiences with both: your comments and preferences...

I understand your grief when it came to your subs amplifiers dyeing on you  My svs did the same just after the warranty ended. Replaced it with newer amplifier and really wasn’t impressed after that. Sold it shortly after...

Guys don't forget JTR and rhythmik servo subs. Both seem quality.

I replaced my JL Audio E-112 (2), with a pair of REL  S/510, due integration  issues. I was running my speakers full range with the subs working underneath, altho the subs sounded very good on some material I just could not eliminate some bass boom and hum. At times I thought it just might be the individual tracks. So I decided to get the REL.s, and the integration, for me, is much better, after getting the subs setup, I no longer have bass issues.  

Sorry and surprised to hear of your problems with your SVS subs.  My two lowly SVS SB12-NSD subwoofers have been cranking for a number of years with no problems, knock wood.

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.