Two small RELs or One Larger Sub

What would you do? 

Dedicated music/listening room -- 16 x 25, with 10 foot ceilings, no openings to other areas.
PSB Imagine T2s
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Strictly 2 channel system.  

I'm looking to add air, space, realism.  Ultimate bottom end is not as important as all the other stuff a good musical sub does for full spectrum floor standers. 

I saw that Upscale had the REL S/2 on sale for $1k ea.  I was thinking it might be prudent to go with 2 of these as opposed to going with one REL S/3 or S5. 

Thoughts?