Actually, this is the time when you should really be enjoying yourself! It's an exciting time, so don't fret and have fun. The subwoofers you have mentioned are all good. Not a bad one out of the bunch. And we will all have our own personal preferences based upon what we've auditioned and purchased. I don't think there is a person here who has tried out every sub you've mentioned.
Two subs are usually used if one cannot solve room mode problems at the seating position. In order to get good frequency response over a larger area to encompass multiple seating positions, many will opt for multiple subs. Of course, two subs are more difficult to set up than one, especially if you buy from different companies. The side benefit of two subs is that it will add 3-6 dB additional output, so each sub will be working with less stress.
I have two subwoofers, but each sub is in different rooms doing different tasks. I found out quickly that I didn't need two subs in either room (and each room is much larger than yours). But all rooms are different, as well as the seating requirements. I'd advise to try one sub at the upper end of your budget to see if that will make you happy … better yet, thrilled. I'm pretty sure that a couple of subs (especially if you swap the SVS SB to a PB) on your list would be more than sufficient in your room volume. But if, for whatever reason, you can't place the sub where it will give you the response you need at the seating positions, then send it back and try two lesser quality subs. Both PSA (for a limited time and only on the XS15se and XV15se) and SVS provide free shipping back to their facility (both provide free shipping to your home).
My preferences? Since I haven't auditioned any of them, I cannot say. I can tell you that I have an SVS sub in one room and a PSA sub in another … and I'm thrilled with both.