Subwoofer Suggestion

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.

I just added dual Rythmik L22s to support my Tekton Pendragons, and I’m very happy with the sound after weeks spent integrating. As stated above, consider rolling off the mains. I use a K231 active crossover at 70-80hz, and this creates incredibly powerful and tight bass from the subs, while allowing the mains to offload the lowest freqs, which cleans up the entire midrange. This method is challenging, and it can sound weak down low until everything is properly dialed in and integrated. Then you have deep bass, clean low-mids, clearer voices, and a sense the bass is truly emanating from the same world as the rest of the music. It’s labor intensive to dial in, but I found it way better than running the mains full range and reinforcing with subs, which led me to different flavors of muddy midrange. This is very system/room dependent, and may not work for you, but hope it helps! Getting bass right makes everything better.

@kulo The REL T/9i retails for $1299 USD. But in my experience you can buy them (I bought two) for a discount from a dealer in the US. I don’t know where you are located. 

I'll give this a try thank you.

As stated above, consider rolling off the mains.

king baracyda I'm located in Philippines, everything here is so expensive compared to US.