I'm working at a studio that just got an SSL 6k console. The way they have it installed, whether you are in record or mix mode on the console, you ALWAYS run through the DAW (for me, sonar. For them, Nuendo).
To clarify- when you run something through the board, you hear nothing unless it passes through the DAW.

I have always utilized hardware monitoring that is latency free, except when using vst guitar amps or when using VSTi via midi. I find it hard to believe that there isn't a better way to use the board.
After adding some plugins, the client reported delay in his cans. I tried using PDC, which does help, but it's annoying to have to switch it off every time you want to listen back, and more importantly- it makes punching-in impossible! Either the existing material is out of time, or the incoming signal is out of time. It's maddening. I had to hit the FX button that disables all plugins in order to finish the session.

These guys that run this studio know their stuff. I have a long way to go to catch up with their knowledge and engineering skill, but am I right on this one?

Hi. Which plugins did you add? Some plugins (with look-ahead feature) introduces latency no matter what.
I'd use as "light" plugins as possible during tracking.
All the best.

The board for sure is capable of direct monitoring. You might have to spend time with the manual. They may have never had to use it because my guess, they are using Macs via Thunderbolt and have lower RTL . 
But there will be a way to set up the board to play back Sonar, and monitor an input with in the Solo or cue mix settings. 

They don't use Mac.
They use antelope Orion usb interface, rme MADI card for AD, and I forget the name of the clock they're using.
Windows and Nuendo

Are you using the same set up but running Sonar as the only thing different?  
That system should be very low latency. I wouldn't use plug ins while tracking myself, I would be inclined to use the mixers reverb if needed. You might wish to "print" all tracks and bypass effects. 

From the setup you are describing, it might help your thought and routing process if you look at the SSL 6K as a preamp as opposed to an interface.

Yes, the SSL is not an interface and I'm definitely not thinking of it that way- however, the way it's wired in currently, you CANNOT hear sound through the board until after it's gone through the sound card AND DAW!
The DAW and interface are in-between the inputs and the outputs!  I understand why it was dnoe this way when recording to tape, it's ingenious because you can choose MIX or Record modes to control whether the pres, eq, and dynamics are effecting what is going to tape or from tape with the press of a single button.  However, Tape machines didn't introduce any latency.  
The DAW does once plugins are introduced.

What difference?

If your' daw's interface has hadware monitoring there would be no latency. A matter of routing the daw's input directly to the output essentially...

I'm afraid I'm not doing a great job explaining this. Complicating matters is the fact that the SSL, while flexible and powerful in it's routing, can't compare to modern and digital mixers.  
 
It may take a TON of patch cables to make it happen, but it might be possible to utilize hardware monitoring.  However, the console is wired a certain way right now (under the hood where things are not easily accessible) and no one else using the studio is interested in utilizing hardware monitoring with no latency (yet....).    
 
The software mixer (from RME for the MADI card) may be the answer.  I use a similar version in my home studio that also has zero latency FX built in.  This paired with the insane patch bay may contain a solution (thus the patch cables)
 
Some sessions, I will use the SSL in the old school way, mix through the board, and commit the mix to "tape" (DAW).
There is an ancient computerized Recall system that doesn't include motorized anything, but I don't think I have the patience for it, nor do most of my clients.  Judge if you must.
 
In any event, I'm grateful to everyone who commented and I'll try to update this after I've progressed!