ReL Subs: High Level or Low Level connection

FYI, I have Anaylsis Plus cables with Speakons for the REL subs. The cables don't work with 2 pairs of spades on my Pass INT-25 (probably the same on your INT-60) due to the plastic protection caps on the speaker terminals.  You can run the sub cables off the speaker instead.  That also saves on cable length.

You likely already know this, but I forgot to say that the crossover setting on the sub is critical to getting it integrated.  Obviously it’s speaker dependent but I started with mine too low.  

Initially, I agree with lalitk. I'll say my extremely short lived experience with REL  favored using the low level signal.

Relocating the sub-bass speaker and equalizing the low level signal greatly improved every aspect of the product. Except for its dramatic -6dB roll off beginning in the mid 30Hz region. It remained void of any worthwhile desirable and delicate subsonic output present on many recordings. A degree of which is provided by most all -3dB subwoofers.

Personal taste is everything.

@oddiofyl and @jastralfu, what crossover level setting would you recommend?

I too, have a single Rel S510, and my speakers are 3-way, floorstanders (PMC Fact 12s). My integrated is darTZeel LHC-208 Mk2. Currently I have the crossover at 40Hz. Would appreciate your inpout.

I attach 2 RELs together with AQ screw-on spades to attach to the amp, currently a Pass XA-25. Low level inputs on the RELs have never interested me as you need long RCAs which are generally a bad idea, and the high level makes more sense.