1. You'll need the quad 2 ohm 15 to run it with that amp. RE X.X.X are typically dual 2 ohm subs, and the MA amp only puts out 1200 when wired to 2 ohms.
2. You won't be underpowering the sub. 1600W RMS is a thermal rating, the subwoofer will reach full excursion with less power than that depending on the enclosure (typically 600-800W RMS with the XBL^2 drivers with larger sealed enclosures) so depending on the box you may actually be overdriving the suspension.