I just set up a S/510 for my Dad. Its a really nice sub. I have an older r305 which has been rock solid , on for the past 15 years or so... continuously.
The S/510 sounds excellent with a 2 channel source. I have it crossed over around 60 Hz and have his Sonus Faber Electa Amator III running full range. Sounds phenomenal.
In larger rooms a S/812 might be a better choice but I was really surprised at the output and how it sounds.
The great thing about these subs is the speaker or line level connections can be "mixed" with the .1 LFE input. This is such a great and important feature for those using a sub in a mixed 2 ch and surround set up. I can not emphasize how important that is in achieving balance between the two.