Subwoofers.... one 10" or two 8"?

        I have an  Sunfire hsu12 .( az cable rca's from preout) I am pretty impressed with it in general .Althoough i did put 3 . 1.5" audiopoints under it which just made a real deal difference in the overall sound ).I would consider grabbing another, which is somewhat shocking to me with it being a 12"in the grand price range . i have generally preferred a pair of 10".If i had the money i would buy the jl audios probly 10". For yrs we tauted there power in audio apps and boats etc. There new subs are serious but are like 3-5k a pair.The sunfire ,svs rythmic etc would much less.
       Like i said Larstusor hook that 8" up and see what you get then let us know whats happening (easy to resale that sub).
       Also op  has limits on treatment and wife constraints as many do
.      Eric
 Although i do run a big velodyne 15" in my ht room its huge front ported. that hsu has to rattle the walls,my velo is nuts just not a good audio sub imo ..i would go sealed myself

Dealer alert;   Current velodynes are sealed subs and are designed to play very low frequency 20 and below).  I use 2 10"'s for my room (dd10+ series ) which is 28x30 and 15 foot ceilings, which is a lot of cubic feet. 
I cross them over at 40hz from my TAD CR1'S.  
I probably should have gone with 12's or 15's but wanted to keep form factor as small as possible.   
I would suggest to OP that he buy one high quality 10"sub then add another as funds allow.   This way he'll have deep bass with one, then smoother bass when he adds the second. 
Anyone in NYC that wants to hear the velodyne dd10+ series contact me at Triodepicturesound.      

If you can phase the sub perfectly to the mains you can get a lot more impact from even a small sub. This requires a sub with a continuous phase adjustment. (Not just 0 degrees or 180 degrees.) If your prepro can’t set a delay for the mains the best you can do is time align the sub 1 cycle late which is totally acceptable. Check: http://www.soundoctor.com/whitepapers/subs.htm
Play a pure tone at the crossover frequency with cable polarity reversed on main, dial phase on sub till you hear the null at listening position. Now perfectly out of phase. Switch to correct polarity on cable to main and now is perfectly in phase. Can’t overemphasize the importance of time alignment to SQ. Consider that a crossover or low pass filter at say 12 db per octave gives very large area of overlap. (40 Hz to 80 Hz is 1 octave. 60 Hz to 120 Hz is 1 octave) If the timing is out of alignment there is distortion of all the sound waves over a wide frequency range (partial cancellations and partial additions within each sound wave). Sounds like hell. Anyway, I have several systems going and several really good subs. Needed a sub for a 2 channel setup so I got a single 8" JL Audio Dominion D108, Just to add a little bottom to my "full range" Revel Performa F206s. Totally did the job in a 17’ x25’ room. Couldn’t believe it. Didn’t want to believe it (cause I wanted to justify a bigger sub purchase) Was not great until I phased it in however. Go ahead and scoff ye unbelievers! Went ahead an got a Revel Performa B110 sub anyway because it was prettier and the price was ridiculous. But can’t really say the resulting SQ is remarkably better, even though It does go a little lower. Set up properly the performance of a pair of JL Audio Dominions would beat any 10 sub that was set up improperly IMHO. :)
But them ain’t your grandpa’s 8" subwoofers.

Due to "group delay" sound impulse leaves the sub usually 8-10 msec later than it leaves the main, even though the electrical impulse hits the sub and the main at the same time. So must be aligned by ear. Using just distance measurement doesn't work. Used to think there was something wrong with my autocalibration when it consistently made sub setting farther away than the actual measurement. Check:
http://www.theabsolutesound.com/articles/subwoofer-basics/?page=3