Dbld- I have heard this too. I think the reason people might say this is because the Mac is truly a 'balanced' connection. Meaning very simply, each pin breaks off into it's own path, they are not combined inside. So....If you have a preamp that is not truly balanced, it makes no sense to use Balanced, and you would most likely get better results with the RCA connection. I have a 5.5, and it is truly balanced.
So I took this one step further tonight and put the Mac in the place my Krell is currently in. Last night I had it just sitting out in the middle of the room, and it was an eyesore. So it is in the place it would live in my system now...I have to say, I like the way it looks ALOT better this way, I was a little skeptical before since this thing looks a little Spartan. I can see why people match up all Mac stuff, looks great. Kind of a status symbol ehh??
Anway, I am listening, listening and listening this eve...Allison Kraus (Union Station) right now, very nice. Amp is alot slower than Krell though, no doubt.