Krell KRC3 preamp

Thank you. Is this the only way to do this? 
Is it possible to do it without Goldpoint SW4? 
I read this in a review but don't understand it: 

"Input S-3’s hidden potential is to act as a unity gain stage, perfect for explaining its complete label of ‘S-3/Proc’. ‘Proc’, of course, is short for ‘processor’, meaning surround-sound. If configured for the latter through the internal switch (the standard setting is as a conventional line input), the KRC-3’s volume control and balance are disabled when the S-3/Proc input is chosen. In this mode, the overall system level is accessed through the surround sound processor. Naturally, this leaves two-channel operation through the other inputs absolutely untainted by force-feeding through the surround-sound unit – a true by-pass for purist stereo listening" 

Seems there is a way to do it, but not sure how to connect it in this way. There is more about this in the manual online, but still difficult to understand. Can someone please explain

I appreciate your input. 

Which way is better? Do you know what the pros and cons of either way? Would you use the S3 on the krell if you were in my situation? 

Also, if I wanted to compare the Preamp section of Mx135 and KRC3, is it possible to connect as you mentioned above, but also,  add  RCA connections from MX135 to the amp RCA? Would that work? 

can you please answer the second part of my question about additional RCA connections from MX135 to my amp? Or am I confusing you?