If you can afford it, I recommend starting with one PC13-Ultra and see how you like it. Then, if it is not enough for you, buy a second PC13-Ultra. If you went with two lessor subs, it would be much more expensive to upgrade than to upgrade from one PC13-Ultra.
I also recommend that you talk with the people at SVS and see what they think of the idea of one PC13-Ultra versus two PC12-Pluses. But remember, the PC13-Ultra is supposed to go deeper, and you will basically just be getting more output with two subwoofers, not deeper bass. So for me, there is no way I would go with a pair of PC12-Pluses instead of a PC13-Ultra.
As for your main speakers, although they are supposed to have output down to 12 Hz, the -3dB point is 30 Hz. So, if you like really deep bass, and you want it as loud as it should be, a good quality subwoofer would be a good idea. And with those speakers, there would be no point in a cheap subwoofer, because they already go pretty low. But for many people, the amount of bass you can get from those speakers is enough. So, whether you would be happy without a subwoofer or not is hard to say, but I would want a good subwoofer in your situation if I could afford it. My advice above is, in my opinion, particularly relevant in your case, as you are just wanting deeper bass, not so much more bass. If your receiver allows for different crossover settings for different channels, you could set the crossover for the main speakers pretty low, which would enable your subwoofer to concentrate on just really deep bass, not on all of the bass.
I must point out that a member of the AVSForum did a comparsion between 2 smaller subs and 1 larger and the 2 smaller subs won.
And what were the standards for "winning"? If you are talking about more output, then it would not be surprising if two PC12-Pluses "beat" one PC13-Ultra. But the simple fact is, (aside from a pair of Pluses costing more, so they
should win), according to SVS, the PC13-Ultra goes deeper before one hits the - 3 dB point.
Also, of course, in some rooms, it may work out better to flatten the response with two well placed subwoofers, so which will be "best" in a given situation is going to depend upon the room and placement as well how many and which subwoofers we are talking about.
It is also worth pointing out the first five words of my post, "If you can afford it...", which, of course, is limiting the applicability of what follows. If rbj9 can afford to buy an Ultra now and one later if the first one does not work well enough, then buying one Ultra now is a good plan. Surely, you will agree that getting two PC13-Ultras is better than getting two PC12-Pluses?
And if rbj9 buys the two Pluses, and wants to upgrade, it will probably be to replace one or both of the Pluses (presumably, there are some space limitations for the number of subwoofers in the room), which will be expensive, whereas with adding a second Ultra, the first Ultra is kept, so no money is wasted.
I suggest you get the 2 small subs and then if you need the deep stuff you can get a sub that specializes in low lfe.
You are now talking about buying three subwoofers, which is likely to cost more than buying two Ultras (not to mention the extra space it will take up).
Or you could just DIY and have the best bang for your buck.
That may be, but that is an entirely different matter from whether it is better to start with an Ultra or two Pluses.
Obviously, people who want more output, and do not require deeper bass, would be better off with two Pluses than one Ultra (this is assuming that two Pluses really will play louder than two Ultras, which is likely true, though I have not seen any proof of this). But not everyone is wanting more output, but is instead looking for the deepest bass reasonably possible. So at the end of the day, we are talking about preferences, and rbj9 must decide what is most important to rbj9. I would go with the single Ultra to start, for the reasons already stated. Other people would go with a pair of Pluses. I am
not saying that they are necessarily
wrong to have that preference. But it does involve a preference that I do not share. I want the deepest bass reasonably possible, so the Ultra, for me, is a better choice.
