Subwoofer advice

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.

$1000.  

At that price, I would considering follow Tim's suggestion of a pair of PB-1000s.  Personally, at that price, I would do either 1) a pair of Hsu VTF-2 MK5 (but you give up the variable phase control), or if I could stretch to $1,200 a pair of Rythmik LV12F.  

Another alternative if you are willing to DIY, is a Dayton Audio SA1000 subwoofer amplifier ($400) and a pair of Dayton Audio 15 Ultimax Subwoofer Kits ($640 for the pair).   

You have a relatively large room that to get decent levels of deep bass will need pretty good sized subs.  You will not get room gain from the size of the room until 18hz, so that is out (not to be confused with reinforcement from being near a wall or corner) With the Hsus, Rythmik's and Dayton, you will be able to get 105 db of clean output at 20hz, the PB-1000s will have less capability. 

I really do suggest in high passing your mains, it makes integration easier and will allow you to focus the placement of the subs for the best bass and your mains for the best imaging.  

I would get the HSU VTF-3.