2 subs connected to a 2 channel amp?

Before you buy any subs I would call the Manufacturer and see if the high level input will work with the r300. When I called Hsu Dr. Hsu actually answered the phone. Very happy with my ULS-15's! 

If you use the sub out of the node and use the volume control of the node you would have to you the pre-in on the r300 bypassing the preamp in the r300.

Otherwise, the volume control of the r300 would change the volume of the speakers but not the subs. Also, the subs would only work with the node and not any other source.