From Doug a few months back. I normally wouldn't paste in an email but we're not dealing with a controversy here I don't think, just clarification. Modded or not the line stage sounds great to me.
"Marc, the first year or so I did upgrade both. However, most folks didn't care to pay for a line in upgrade so I dropped it along with the price of the upgrade. Now only the mic in is upgraded.
Most tapers like to have a modded 661 for the times they do not use an external preamp so most tapers order upgraded 661s. BTW, I like line 2 in for use with an external preamp, the only downside is no locking connector. Sometimes we have plenty of space to setup, other times space is insanely tight, that's when I demand locking connectors and my gear in a beer/soda spill proof bag.
I hope this helps....Doug."