REL Vs SVS for 2 channel music listening

I don't think the subwoofer is the issue, but rather the interaction with the room. Just look at some REW waterfall plots. Subwoofers produce low frequencies and hence room modes. To cure this you need a larger room (because in a large room room modes occur at lower and hence less obnoxious frequencies), use multiple subs (two are often enough) to even out the response over a larger area, and use dsp room equalization such as the DSPeaker Antimode 8033.
At your budget I would get two SVS SB1000 subs plus an Antimode 8033. If your room is large I would save up for two SB2000 subs.
For some reading material, see here: http://www.acousticfrontiers.com/20101029using-multiple-subwoofers-to-improve-bass-the-welti-devanti...

I agree with about 98.5% of what akg_ca just posted. The short version might be, pick a very good stereo speaker system that integrates a sub and amp into the design first. If you do not do this you must find an additional subwoofer/low bass system that is engineered very well, like Vandersteen, and pay top dollar to get that tight musical well integrated bass. Cheap subs will really make your musical experience worse....IMO.

I’m not advocating a separate sub rather than integral sub in the primary speaker design. Want only to comment about recent experience w/SVS. Have a pair of SVS SB1000s running with Silverline Prelude Pluses. The integration is seamless. A couple of tracks with intricate and agile bass work are on Andy Summers’ "The Last Dance of Mr. X".  Tony Levin's bass on Afro Blue & Footprints, for example, is very musical and fast. The image is very stable. The bass sound is absolutely not directional. It’s impossible to tell whether notes come from the sub or floor standers. They are suspended in space between the speakers. The SB1000 provides line level AND speaker level input. Not all their models offer speaker level input. Continuous Volume, Phase and Crossover adjustment make the subs very flexible.  The right channel sub did die a few (months?) after getting it. SVS provided a replacement very quickly. They might not have had good customer service in the past. My experience with them, however, has been excellent. They have responded to technical questions and dealt with the replacement issue. Their products have a 5 year warranty.  They provide a 45 day in home audition and pay freight both ways if you decide not to keep it.  If I had discretionary cash in abundance would love a pair of RELs - if only for the nice finish those have.  SVS is any color as long as it's black - matt black oak or piano gloss black (they might offer white too now). The "budget" finish look is my only complaint. Very happy with music produced by the Preludes supported by these subs.  Good luck with your decision.

Good to see Hsu Research mentioned. SVS is terrific. 

One not mentioned is Outlaw Audio. If you haven't already, you may want to check their subs out, especially if price point is a driving force.

I've had mixed results with subs. When done well, you will not know they exist until you remove them from the mix. Note that is subs with an s. 

Not sure if you want take the passive sub way. : )  Mentioning it as an option, since it hasn't come up.

Thanks Ghosthouse. I just want to be clear....I'm not unhappy with the bass, low end I have. In fact, I think it's great. I'm not purchasing because I feel something is "missing" more so at times I love really deep strong bass (I can turn sub off If I choose). Deep classical organ to EDM. My musical taste is varied. Coming from a subwoofer a few years back in my 2 channel system, it's really something I like and it "adds" to my listening experience. I was running 2.1 until we moved into a townhome about 10 years ago. We moved back into a house we purchased 4 years ago and I can now happily add a sub back into the mix. So yes, I love how balanced my system is now. In fact, it's the best I have heard except for a couple of other's systems I was able to listen. So while I appreciate the room advice etc( I have my room dialed in nice), I'm just wanting to induulge myself in to the world of heavy bass at times :)