Older vs. newer REL subs

I'm torn on what to upgrade with.

One of my R218's broke and I haven't had much luck fixing or finding a 2nd used one.  In my haste I bought two T5x and for 2 channel music and it's pretty good and is satisfying enough.  I compared it to my one working R218 and the R218 definitely hits harder.  Not trying to chase bass for music hence going with the T5x pair (for cost and enough dynamics)

I decide to hook up the R218 for my centre channel after seeing a Youtube on Rel 3D.  WOW!  

One thing I miss is having more HT impact so I'm on the lookout for a pair of S3 SHO (22Hz) which on paper hit lower than the R218 pair (25Hz).  The T5x  can be used for the rear surrounds or in another system.    The new  S/510 (20Hz) is just out of my price range.  The T9x (27Hz) may not be enough.

I believe everyone is forgetting how important the room treatment is especially when it comes to low frequencies. 

A rel T series can sound much better in a treated room than a rel S series in a regular room.

It doesn't matter if the subwoofer is very fast in a room that has no bass absorption --> You will hear the low frequencies reverberation instead of the actual sound getting from the speaker.  Of course you will also hear the reverberation of the main speakers. 

The dealers usually have treated rooms in which you can hear the differences between S and T series but at home the difference may be minimal and more related to price and placebo effect. 

To make an idea: a subwoofer can sound 2 or 3 times better in a treated room than in a regular room, so save some budget for low frequency absorption too. 

I am also interested in this subject and how does R-328 compare with a T series.

The R-328 is powered by a 350W class D amplifier but it's an older model (The R series is the equivalent of the newer S series)

T9x is powered by a 300W class AB amplifier

T7x = 200 W class AB amplifier

The class D amplifiers are "faster" because they have a much better damping control than class AB amplifiers.

The price of a second hand R-328 is close to the price of a new T9x

I suspect that the R-328 is a bit faster and better than the T9x (also based on the specs) but is there anyone that listened to both in the same room?

@hilde45 What ended up happening when you got the Rhythmic Sub in?

@shahram I got two Rythmik subs. In addition to the REL, I was able to position and adjust them to within +/- 4db between 20 and 400 Hz. Sounds excellent. The Rythmiks' adjustable phase was what made it all possible.