How do SVS subwoofers compare to REL?


I'm looking for subwoofers (one or two) that have a very "tight" natural sound and are not overly boomy. In the future I hope to pair them with some Magnepan speakers. Magnepans are known for having a natural sound, and I want to compliment that.

I've been told that the REL subwoofers (e.g.,T/9i or S/3 SHO, etc., are a good match for Magnepan speakers. However, SVS subwoofers have also been recommended to me.

I don't have any background in high-end audio, so I am interested in opinions of folks here. Are SVS subwoofers considered generally as good as REL in regard to the features I'm interested in? Is either clearly superior? (I had never heard of SVS before yesterday.)

Which subwoofer size (in REL or SVS) would be a good match for a pair of Magnepan 1.7i in an 18 foot x 15 foot room (ceiling about 10 feet) with carpet on floor?

I'm looking at these so far:

REL T/9i Subwoofer about $1300
REL Acoustics S/3 SHO Subwoofer (Super High Output) about $2100
SVS SB-4000 13.5" 1200W about $1600
Any other recommendations?

Total subwoofer budget is around $2600 max. ($2000 or less would be better.)

Also, I believe it is better to buy two smaller subwoofers, compared to one larger one, right? (I'm just not sure where I would put two. Placing one is easier in this room. And I plan to connect everything with speaker wires, not wireless.)

Thanks

lowoverdrive
lowoverdrive, the SB-2000 is nearly twice the price as the SB-12NSD, so overall the difference probably should be expected.  I once called SVS asking about the difference in these two subs, and the difference between the perceived output of the two per the gentleman I talked with was surprising (in favor of the SB-2000) for only a 100 watt amp difference.  Must be other factors, like speaker design, at play.
I have the Maggie 1.7is driven by the Emotiva XPA-2 Gen3 with a Conrad-Johnson PV-10AR preamp.  I have a VERY open listening room - 20ft of open space behind left speaker and 10ft of slightly less open on right. So they sounded good but had no bass impact and depth really at all. As I hadn't expected to buy the amp (one of my bridged NAD214s shat itself before I bought the Maggies and I listen very loud all the time so one 214 couldn't hack it), my subwoofer budget was very limited. I took a punt on a pair Emotiva Airmotiv S10s and, once I got all the setting right for my tastes the whole system sounds just incredible. I have the Airmotivs more-or-less centered behind each speaker with very little phase delay at about half volume and 100hz-ish crossover. Super detailed and impactful bass and the Maggies seem to have better imaging, soundstage, depth, and more of the trademark "soaring" quality. For a "budget" system I think it's superb and my mates are blown away by it.   
I own Magnepan .7s powered by Sunfire gear. 400 watts/channel x 7.

With the Maggie's I round out the bottom end with two SVS PC 4000s and an Earthquake MKV 15 for the rear sub.

While the Earthquake hits hard between around 40-80 Hz, the SVS are ruler flat down to 16 Hz.

The SVS are easily fast enough to compliment the Magnepan.

I'm happy.

I hope this helps.

Div Nanjappa
I bought a SB3000 and a Rythmik F12G to see if I could get the performance I wanted from my mains (strictly 2 channel).  I liked the SVS because it had an app that made it easy to adjust with my iphone or ipad.  The Rythmik ended up being the better sounding sub in a blind test.  It just seemed quicker and less like a separate part of the system.  In the end I upgraded my mains and am very satisfied...for now ;) 
FWIW I owned a Rel S/3 and would vote it 3rd place.  I think the cheaper Rel's are the Bose of subs. They market themselves as unique but they are not.
Former REL owner here. Get a Rythmik F12. You will not be disappointed. They integrate just as well as REL and you get more for your money. Lower extension and musical, tight bass. I like REL subs but Rythmik is just better IMHO.