Subwoofer advice

So looking to add a new component (or 2) to my system (Snell Type D, McCormack .5 or Jolida 502b, Schiit Saga pre, Rega Planet, Dual 1219 TT) and contemplating a sub.  Basement room is 14'w x 30'l x 7.5'h and treated with first reflection points and base traps on front wall.  Interested in the REL T series, either the T7i or T9i.  The Snells have 8" woofers so not sure the T7i at 8" will make a significant difference.  The room might be too big as well.  So it might have to be the T9i at 10".  Looking to supplement clean low end not anything bloated or overbearing.  

Any thoughts greatly appreciated!
Rel or Sumiko is a good choice!  The T9i is great!  I would also take a look at the Sumiko S10 at TMR for $750...

2 are definitely better than 1 so keep that in mind as well
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Hello pkatsuleas,

     I notice you seem to have 2 amp setups, a tube setup with a Jolida tube integrated amp and a solid-state separates setup with a ss Schiit preamp and a ss McCormak .5 amp.  
     All good stuff but I need a bit more info before I can offer meaningful advice:
1. Do you alternate use between both of these systems?

2. Are they used for music only or do you also use for some form of home theater audio?

3. What's your budget range minimum to maximum?

4. REL are nice subs but there are other high quality subs at more reasonable prices.  Are you willing to use other brands of subs?

5. Are your speakers set up along the long 30' wall or the shorter 14' wall?

My two cents. You aren’t getting much by going to the Rel T9i, their -6db point is 28hz and they are expensive for what you get. If it were me, assuming at $2,200 budget (the cost of 2 T9i on sale) I would do the following:

1) Purchase a HSU High Pass filter for $100.00 to run between your preamp and amp for the Snells. Roll the Snells off below 80hz to relieve them of the deep bass duties.

2) Purchase two subwoofers, either 1) a pair of Rythmik F12 ($1960 a pair), or 2) a pair of SVS SB3000 ($1999 a pair).

The Rythmiks offer a bit of a tighter, drier sound, with one band of parametric eq. The SVS have a three band parametric. With the Rythmik, you can use the parametric to treat your primary mode peak at 37 hz, with the SVS, you can treat that and the second at 56hz. Fortunately because your room is pretty large, you will have less mode issues than most, the primary being driven by your ceiling height.

Either pair of subs will give you far more adjustability than the RELs (which offers no parametric), far greater output, and true flat response down to 20hz. Relieving the Snell’s of deep bass will allow them to play cleaner and sound more open.

Enjoy, the Snell D speakers are one of my all time favorite speakers.
Should have known to provide more info!  Noble, the rig I am using right now is the Schiit Saga (tube/passive) with the McCormack.  Sounds great but I know the tubes will be calling me back eventually.  2 channel only.  Budget really is $1k but could stretch just a bit.  Been looking at used but nothing good yet.  Missed a local HSU that seemed promising.  Not stuck on REL, just seems a safe bet from the research I've done so far.  And recommendations from a few dealers, one who doesn't even sell REL.  Speakers on the short wall pulled out about 4'.

Mcreyn, I have been researching the high pass filter and one day I might go that route.  Does seem like the most logical way to maximize potential.  For now I would just like to get a sub in my system to experiment.  I will look deeper into the SVS.  Thanks for the knowledge! 

And yes, love the Type D.  Spent $700 on them 10yrs ago and they've been great.  Auditioned many more in the sub $2k range and for me they were the favorite.  The McCormack tightened everything up and makes them shine even more.  The Saga pre at close-out B stock pricing was a big surprise!  Sounds great