I echo kgb's thoughts here. The MKV-15 will actually give you slightly more SPL, but will sound much closer to the top of the line sealed subs for music. Not only that, no matter how loud you play it, you will never bottom out the driver and you will never hear any port noise.
![Wink ;) ;)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
It's only about 17" cubed in size.
That said the Plus/2 I'm sure will more than meet your requirements as well.