Which subwoofer should I buy? Help Please

Looking for a good powered sub with small footprint.

Have the following in mind:
Earthquake MKIV10
Sunfire True Sub MK II
Sunfire True Sub Jr.
Carver Knight Shadow
Yamaha YSTSW-215

Earthquake is the biggest I will go (14" cube)

Sunfire True Sub MK II, I heard it's slow and not good for music?

Sunfire True Sub Jr., I favorite this one the most. Smallest footprint, 9 inches cube, but quite expensive...
How much do they usually go for (for used ones)?

Carver Shadow Knight, made before Bob left Carver. Also a subwoofer with a super long throw driver. Extremely similar with Sunfire subs. Sells for only $300 used and if it perform like the Sunfires, it will save me some money.

Yamaha YSTSW-215, cheapest, heard they are okay. I might need 2 of them if it's not enough. Will still have money left if I buy 2... Sounds good... but sound-quality-wise?

Really don't know what to buy. $550 is the max I can afford... Please help...