My guess...2 channel. How about a stereo amp and preamp to be a companion to, or replacement of, the RR-2150? And maybe a full range speaker too.
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AvFan
Outlaw 976 | ATI 2005 | M&K 850s Left, Center & Right, Surround-55s, MX-70B Sub | Harmony 950 remote | Panamax 5100 | OPPO UDP-203 | LG OLED55B7