Looking For A Subwoofer

with a small footprint(max about 12" square),speaker level INput  & speaker level OUTput.Would like to keep it under $500.00 but might go to $1000.00 for the right sub....Thanks much,take care...
How "hard" is your 12" limit, free diver?  An SVS' SB1000 - a sealed sub rated into mid 20 Hz - is right around 13" cubed.  It has speaker in and out as well as line level connections.  Price is also in line with your budget.  Worth noting, the next SVS model up has line level connections only.  
Sunfire 8" sub.
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Hsu 12", $512

Having said this, without EQ, smaller subs are better. Maybe even a 10" such as this one.

My Spiel:
Subwoofer's are not plug and play.  The deeper they go the more likely to run into room interaction issues. Placement, EQ and bass traps are often needed.  If none of those are items you can spend time and money on, smaller is safer.


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Look into the REL S/2 subwoofer.


They retail at $1499 and some dealers have these on sale right now for 1/2 price. 

JL Audio D108.  
Sounds musical because it has a flat usable frequency response and is not a one note wonder.  
Also has all the features needed for perfect integration including a continuous phase angle adjustment and speaker level inputs.  
+1 SVS SB 1000 !
Wonder if the OP finally made a purchase.  Did get a pair of SB1000s.  Am happier than the proverbial pig with how things are sounding.