can subwoofers make things worse?

Short answer: "Yes". If you reside in a multi-family dwelling, a subwoofer can make the relationship with your adjacent neighbors worse.

+1 @wolf_garcia Explains what I mentioned as sound stage expansion.

Rel T series don't move air and shake room, roll off bass in lowest registers. As others have mentioned neighbors can be a very real concern, I was the one calling police on a very careless neighbor! So, not wanting to bother my neighbors was a major concern when purchasing  these subs, I stood outside my house and not really much more boom than my Klipschorns without subs. Subs with lower reach and capable of much greater output will have much greater chance of bothering neighbors. My Genesis sub moves air and shakes room, makes it unusable in my situation.

Sub placement will be key in a small room.  Try to locate the sub(s) anywhere but in-between the main speakers.  

I've been around subwoofers since M&K first introduced them in mid-70s. I've used them with lots of speakers, large and small including Magnepans and KEF LS-50s, both notoriously difficult to get 'right' with subs. Two major success criteria:

1) the HP and LP filter should must be used, and set as low as possible. Typically no higher than 60Hz for music, and 80 Hz for Home Theater. The HP keeps the low bass out of the mains, improving their dynamics and power handling, by reducing their low bass load. OThis means no speaker-level connection - your preamp needs a Sub Out with bass management, or the sub itself needs line level inputs and HP line level outputs back to your power amp. The latter usually limits placement options, however. 

2) Placement and level settings will take some effort. However, same wall as your main speakers, roughly 25-40% of the way across the wall is a good starting point.

Listen to both male and female vocals first to make sure the sub isn't adding mud or chestiness, then to material with true bass, (Beyond The Missouri Sky, Pat Metheny & Charlie Haden) then sub-bass (I Believe When I Fall In Love, Stevie Wonder). Most people have never heard the pitch, tone, and texture of Charlie Haden's bass done properly or the sub-bass synth line that underpins that Stevie Wonder cut. A good sub, well placed will reveal what's actually on those cuts. 

Either the T/5 (or T/7) or the Micro 3000 are excellent choices for your system. The KC62 I would recommend if you had LS-50s.

Small rooms are always the source of the a lot of issues, as the bass wavelengths are longer than the room itself.  So is also our visually driven tendency to want to put a sub in a symmetrical location- half way between our mains for example.

So subs will excite some kind of room mode no matter what.    The issue is what do we do to mitigate that.  There are many solutions from bass traps to EQ.  My experience is that using more subs turned down low is better than one big one.  For example I would rather go into a small room with 4 cheap subs placed at different distances along the four walls of the room than one sub in corner.  

I think Duke had the right idea with his swarm product.  Also bass arrays work well, in small rooms or large, Bag End did a lot of work on that.  

So we have more trouble with clients buying one sub that we do with clients buying two.  Almost no problems with people buying 3 or 4.  With ATMOS this is a big issue, as much of the basic ATMOS info says subs in front but that doesn't really work in practice.