Yet another Sub Question

I had recently bought and added a Rel S510 to my system. The upgrade was so noticeable and uplifting, I added a second one a week later and never regretted. Everything works more in coherent and the soundstage is amazing.One is good, two is excellent.

I have one subwoofer and it took weeks to find that perfect spot, but with two subwoofers, it definitely makes positioning much easier.

"I have one subwoofer and it took weeks to find that perfect spot, but with two subwoofers, it definitely makes positioning much easier."

I have 4 subs in a distributed bass array and positioning almost doesn't matter.

I have S/510's.  The second sub is like @vicdior says, noticeable and uplifting.  Having 2 subs makes the positioning less critical.

I use the longbow wireless transmitters, it makes placing the subs even easier without wires.  

Definitely add a second sub.

If your goal to simply bolster your current presentation adding another -6dB Sub-Bass speaker should provide a noticeable difference.

REL, "subwoofers (I still like our original term Sub Bass System for its more complete description of what we do)"...

If you're interested in increasing the detail of the presentation as well as the addition of the delicate extra low fundamental frequencies found on many of todays modern recordings there are a number of economical -3dB subwoofer/s available. Positioning within your rooms standing wave bass mode/s, would be required for their optimum performance.

Actual subwoofers are adjusted, not matched, to integrate with any speaker choice.