Hi Annapl,
What Prateek says is right when you are comparing a big sub with18 inch divers with a single 15 inch sub is an unequal comparision. SVS subs are tuned more for deeper extension rather than midbass. It's good that you have a dedicated media room since most of us would have a choice between a big sub or us to stay in the house.
From what I have heard, the job of a swoofer is to produce the low frequencies which your fronts cannot produce. Generally it is the job of the fronts to produce the mid bass. Now if a subwoofer gives midbass then it would be especially useful for people with small bookshelf rather than those having big floorstanders which anyways do the mid bass job.
Using words such as "crap" is truly misleadling & may have impressions on either the product or the person who may not know how to place it. I am not saying that SVS makes the best subs . I am sure there are other companies who offer better products at a better price. But the fact is that they make decent subs with great after sales service. I am not saying this because I too have an SVS sub but the fact is that it does its job very well.
I too prefer trying other brands in general within my budget, be it amps/cd players or speakers & I am not an SVS fan. But I like the build quality of their sub & their after sales service is especially superb. They will never push you to buy an expensive model when a cheaper one will work for your room. In a fair sense lets not put down a decent product so badly without giving it a proper chance.
It may not have worked for few but at the same time it has worked well for some. Apparently the 2000 pro series have been tuned for more mid bass.
Anyways enjoy the JBL as it gives you what you were looking for. Just out of curiosity wanted to know whether the lower part of your screen is getting blocked by the sub.
Regards.