A mod4?????? I guess you will string 2 Mod2s together.
Mod1 = 8ohms
Mod2 = 4ohms
What happens when you put 2 Mod2s. I think you will trip the 7125!!!
The usual recommendation is to use "voice-matched" speakers for the LCR. If not, it is better to use the center channel "phantom" mode. The Ref1s are fantastic bookshelf speakers - they will easily handle the "phantom" center. Orb's for surround and back will work fine for movies (just cross them over at 150Hz - trust me on this one - their spec sheet happily leaves out the +-3db points - hate it when mfgs do that).
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BSMNT HT - Oppo DV-970HD,Tos HD-A2,Emo LMC-1/Onkyo TX-SR705, Outlaw 7125,PSB Image 4T 8C 10S, Outlaw LFM-1+,Panny PT-AE900U, DIY 106" fixed screen
LIVRM 2ch - Philips 963SA,Lexicon DC-1,Carver AV-505,Von Schweikert VR-2,Sony KDF-E42A10