I am currently shopping for sub ... i have max of 1200$ for subs . i dont have that much of room either and i dont like having hudge sub too ... i dont like that big box in the living room .... but i do like the big sound tho :S .
ill be using 50/50 for ht and music . i was thinking maybe of buying 2 of those subs ( pb-1000 x2 or LV12R x2 .. or one of each !? )
ill be moving in new house soon , room will be medium sized room ..(1500-3000cu ft)
I have 1 PB-1000 in my apartment living room that is about 12'X15' with 8' ceilings and I think it does great. I would highly recommend them based on my experience. SVS also offers SB-12NSD's (a pair could be had for $1149+tax) which are a bit smaller than the PB-1000's. So you may want to consider getting a pair of those if size matters to you (though I haven't heard them). Also SVS has great customer service/warranties/policies and if you are unhappy for any reason you can return them for full money back within 45 days.
It may also be helpful to know what you are upgrading from, or if you have heard any other subs that you liked/disliked.
It's not crazy to buy only one expensive sub if you know you only have the room for one sub. I'd take one SubMersive HP over two LV12R's any day of the week, but of course that's not comparing apples to apples.