Adding Sub to current system


I currently have a pair of Sonus Faber Electa speakers. These speakers have 6" and 1" drivers respectively and have a 1st order crossover. The popular magazine test disk demonstrate the speakers go down to about 40HZ. I'm interested in what I'm missing below 40HZ besides just a non-musical "BOOM". I know for a price musical Sub's are available, but would it be an exercise in futility trying to integrate a Sub into my system? The spot I would choose for it would be to the left of my speakers in a corner - your thoughts please!
Rpg
rpg
Place the sub out in the almost middle of the room as close to your listening position. It will blend right in with the monitors . In my setup it sounds as if the speakers are actually producing the bass . It is amazing .Also set the crossover very low say 30 and only turn up a few clicks on the dial. Please try this and you will be a happy camper !
I have a rel t2 bought new here for $550.Mated with magnepan 1.6's . i have no desire to upgrade.It sounds that good. The rel t2 was a golden ear award winner in TAS in 2010.
Post removed 
The REL's adjustments obviate an eq. All sub adjustments are based on personal taste responding to room interaction, so you can ignore most opinions from people not residing in your house. Also...it is possible to get low-ish bass from small woofers...I have 3.75" woofers in my Silverline Preludes and they kick ass...the REL just makes everything better.