I'd lean toward the Hsu VTF1.2 since it offers the most set up flexibility, i.e. 32Hz tune, 25Hz tune, & sealed mode. Since your system won't have the benefit of room correction software (Audyssey, YPAO, etc), that will help you adjust the sub to your room / taste.
As for sealed vs ported, here's a little light reading:
http://www.audioholics.com/loudspeaker-design/sealed-vs-ported-subwoofers
The SB1000 is a bit different from the sealed subs characterized there though, as SVS uses DSP to shape its frequency response into what you'd expect from a ported sub.