by "powered" what is really meant is that they are power amplified speakers.
The audio outputs on the back of the receivers are standard RCA Phono "line level" outputs .. 1v P-P so not much power is there .. you would need an Amplifier to boost the signal to make it come out of any standard speakers.
If you don't already have a home theater type amplifier .. you might want to invest in one .. many have "zone 2" and "zone 3" options.. so that you can output audio to different areas. Some mix line level outs and speaker outputs..
my Onkyo is one of those.. I have Zone 2, Zone 3, which are standard line level outs but then there's a set of speaker lugs on the back of the receiver that I can switch to using with Zone 2 ... in stereo @100 Watts ...