Subwoofer Suggestion

@kulo      Just so you know, RSL does not have dealers and they do ship all over the world.  You could do three subs for $1200.  Heck, you might be happy with two!  They really are a great value.

When I brought the kanta 3 home I loved the mids and highs but the bass was a mess, +10db at 100hz and -20 at 80 hz with a little recovery around 60 hz b4 falling off the chart. My room. Moving them to the long wall and playing with boundary placement did smooth them out a lot, but they never did offer much below 70 hz in my room. I would try a single sub between the speakers first and if that don't work then buy the second. A flat measuring speaker isn't necessarily desirable and the Kanta only needs help with the bottom 2 octaves.

Corelli I'll check the rsl subs, I'll take it into consideration thank you.

steve59 may I know the sub you used for your room?

First of all you need a continuous phase control, polarity control and multiple crossover slopes.

Second you need to roll the lows out of the mains. Doubly important with ported mains. This can be a simple 1st order capacitor crossover to the main amp.

Third, a sub with a control app to equalize the bottom to the room can do wonders.

Among others, the Martin Logan x series have all of the above. 

see  http://www.ielogical.com/Audio/SubTerrBlues.php for setup and general sub info. The Finally graph shows the proof of the pudding is in the eating.