Mickey, you wrote "[w]ith regards to the pre, it needs to be matched with an amp with a fairly high input impedance. The Ref 150 SE is listed on the ARC website as having one of 300 kOhms and that should be sufficient. Is that the same with the Ref 150?"
The answer is yes. The specs between the Ref 150 and 150 SE are almost identical. Ditto the GS 150. You should note that the Ref 150 (SE and non-SE) and GS 150 only have XLR inputs ... no RCA/SE jacks.
The answer is yes. The specs between the Ref 150 and 150 SE are almost identical. Ditto the GS 150. You should note that the Ref 150 (SE and non-SE) and GS 150 only have XLR inputs ... no RCA/SE jacks.