Oh this is humiliating...

I forgot that the 630 lets you have different channel settings for different inputs. When set to DVD the FL channel was set to 0dB, but when set to CD the FL channel was +10dB. I read your post again earlier this evening and suddenly I understood what you meant.

Now I just have to figure out why the other surround modes didn't sound so bad

Thanks !!

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8