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!
Dear @pkatsuleas : Inside your budget and with good quality performance the @instlouis advise is with out doubt the best one.

At your room/system seant position you need only two subs  You can try the Golden Ear units for you can have first hand experiences in your room/system. One advantage in the GE subs is that comes with high-pass filter for the Snell stays focus in all frequencies but the low bass and in this way the Snell IMD ( intermodulation distortion. )  will goes down and this permits that the overall system ( speakers/subs/roo. ) shines as never before. I think you will be satisfied with.

Then in the future and after your learning self experiences with subs you can up-grade it with better quality subwoofers because not all subs sounds the same, exist quality grades in between.

Regards and enojoy the MUSIC NOT DISTORTIONS,
+1 @rauliruegas  

OP - My room is 14.4x24 and the GE Forcefield 3's at 50% provide respectful and tight bass . 
Don't know where you're located, but my GE dealer is Speaker & Stereo Store here in St Louis. Wylie Williams has taken care of me for many years and I highly recommend him
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Thanks very much to all of the bassheads!  Great info pretty much in sync with what I've been researching.  A bunch of good suggestions.  Seems like the consensus is 2 subs for my size room - makes sense.  Always wanted to hear Audiokinesis' stuff.  Unfortunately way out of my budget at this time.  Basically, I have around $1500 to blow.  Was thinking a sub and DAC (see other thread in digital).  Really need to get up to speed with digital.  So, its a balancing act.  I started out thinking better sub and an inexpensive DAC like a Dragonfly. Now I'm leaning towards spending a bit more on a good dac/streamer.  

As far as the subs go, there are two local on CL that seem promising - a HSU vtf-3 mk-4 and a SVS pc-2000.  Any opinions there?  Really just want to experiment and start with one before jumping into 2 subs and a high pass filter (pretty sure I will get there eventually!).  I have had good luck with used in the past and it has given me good bang for my buck.

Thanks again
Whatever subwoofer you choose and however subwoofers you decide on, if you don’t want to turn you room into a giant shaker table experiment, isolate the subwoofer(s) from the front end electronics by placing them on springs. Problem solved! 🤗