Laltik, both seem like great preamps. Not knowing an awful lot about the SP-20 I would probably be more partial to the LS28. I think that may be the sweeter of the the two based on some of the reviews I've read.
I didn't get the chance to hear either. I had a REF 5SE and loved it. When the REF 6 came out I thought it might be a better match for my GS150 and based my purchase of the 6 entirely on the strength of REF 5.
I didn't get the chance to hear either. I had a REF 5SE and loved it. When the REF 6 came out I thought it might be a better match for my GS150 and based my purchase of the 6 entirely on the strength of REF 5.