I would strongly recommend the Silver RX-2 speakers rather than the RX-1 for that size room; the RX-1 is way too too small. Adding a sub is not going to make up for the overall lack of audio output power capability from the RX-1.
The 8-inch driver of the RX-2 will do a much better job down to 50 Hz, and then the sub can take over below that. It has nearly twice the cone area of the RX-1, which you definitely need.
Neither of those speakers has much output below 50 Hz, so to produce that bass below 50 Hz you will definitely need a large 12-inch subwoofer with considerable power (300+ RMS watts) for that room; I suggest the Rythmic FV-12 or Klipsch RW-12D.
I personally doubt whether that amplifier has the sound quality or power needed for your application, but if you don't want it to play anything very loud or demanding, it might be OK. In general, the sound quality of Class D amplifiers is poor, and they misbehave when driven hard.
The Music Hall 15.2 is a MUCH better amplifier in terms of sound quality and has more usable power reserves for music peaks.
Edited by commsysman - 7/15/12 at 11:00am