Will these subwoofer be enough ?

Thanks to everyone that responded thus far.  Some great information here.  
I am not looking for booming bass at all and about 70% of the music I play the horns have enough bass for me.   Just wanting to add a little more for certain music but must be seamless and not overbearing but make a noticeable difference if that makes any sense.  
 

thanks to everyone so far and please keep responding with your experiences / opinions. Very helpful 

@hardhattg Your second post only reinforces two REL subs exactly what you're looking for. I was looking for the exact same thing in adding subs to my Khorns. I've had conventional subs with low level connections, dsp, far more powerful bass than the REL's, they always brought attention to themselves through excessive boom or discontinuities with main speakers. With the smaller REL's running at present one wouldn't even know I'm running subs, the integration/coherence makes it sound like Khorns that simply reach lower freq than typical of Khorns. I'd actually rate the improved sound stage as a greater improvement than greater freq range. I wouldn't even call it added bass as I don't have any freq overlap between Khorns and subs. REL's preferred connection scheme via high level speaker binding post means subs flavored by amps to some extent, this adds to the coherency thing.

Anyone have any experience with these specific classic REL subs ? 

@sns   I've had conventional subs with low level connections, dsp, far more powerful bass than the REL's, they always brought attention to themselves through excessive boom or discontinuities with main speakers.

I don't mean to be confronting, would you mind sharing exactly the make and model of conventional subwoofers you're referring to?

Where did you position them within the room?

Anyone have any experience with these specific classic REL subs ? 
 

I have a Classic 98 that I purchased as a demo from TMR. No shame in being honest: I purchased blind and purely for aesthetic reasons to match my Tannoys. 
 

Just wanting to add a little more for certain music but must be seamless and not overbearing but make a noticeable difference

The 98 replaced a Rythmik F12G that had PEQ, variable delay/phase control, low pass slope, crossover, and an extension filter. On the other end of the spectrum is the 98 with just its 0/180 degree phase switch and crossover.

It took me a while to understand all of the settings in the F12 in addition to a lot of experimentation on placement for better integration. F12 is a better subwoofer, but the 98 effortlessly integrated with less localization. I just chalked it up to user error and lack of knowledge on my end in respect to the F12G.

I’m planning to purchase a second 98. In my system the 98 provides that seamless integration and difference in the lower end - the invisible anchor that subtly shows itself when needed in the soundstage (like most good subwoofers). Aesthetics matter to me, and the Classic line helps blend into similar looking speakers and systems.