can subwoofers make things worse?

I can only let you know what happened with our purchase of a set of year-old Quad ESL 57s many eons ago. They were sold to us with a Dalquist EQ-1W sub-woofer with a passive crossover at about 80 Mhz. What happened was the mid-range leaked through the sub-woofer, muddying up that glorious renown mid-range of the Quads. We did not try an active crossover or bi amp the system, which would maybe have made an improvement. My suggestion: just don't.

Kef Kc62 Is good I use that little guy in my kitchen system.

Rel is not good until S models or Carbon special

SVS is for home theater

i use JL Fathom F212’s in my big system. 
look at the JL E Sub

Remember using one Sub can make it worse easier!

it’s easier to integrate a pair of subs properly and balance out the room better

Thank you all for the replies. 

To answer some questions asked of me. It would be used for both, but primarily music - to add the bottom octave my speakers don't reach (48hz - 23khz). 

 The speakers are 2 feet from walls, and 6 feet apart and i sit 5 feet from them, dead center. The speakers "disappear" and fill the whole space in front of me. 

I live in a rented studio apt with no one underneath me. No issue with adjacent neighbors - only the guy who lives above me. He's been pretty cool so far. I wouldn't play the sub loud - just subtle addition of that low bass. 

I barely have room for a tiny single sub. A pair is not possible. 

Ive read recommendations for all 3, but the SVS micro may be the best combination of size, cost, and being able to set it from my listening position. 

Of course - last night i listened to James Taylor and Billy Joel and didnt feel like i needed a sub. Sounded great to me. But the common thought is, as soon as i add a sub ill hear what i was missing. I was told Best Buy Magnolia has SVS and KEF subwoofers. I can try to see them there.

In a heart beat