I can't say that I've ever found the VX-64 to be resource hungry.  Quite the opposite.
 
Are you sure you're not confusing it with the LP-64, which is?

If you're thinking of Craig's video "Sweetening Amp Sims with De-Essing", he used the De-Esser in the VC-64.

Cool. I'll check it out and see how much of a hit the system takes (this project is already running pretty hot). It might do something more beneficial for the leads. The notching and LP/HP really got what little "siminess" of the tracks which is very cool. I'm so obsessive about my guitar sound that I can spend forever trying to get things right if they aren't exactly how I like. Cheers.

Beepster
Thanks sharke. Trying to avoid the really heavy duty/resource hungry ones for track by track use though.

I'm pretty sure the VX vocal strip is pretty lightweight. I use it all the time, on all kinds of sources. It's really handy for getting unwanted hi hat signal out of other drum mics. So I often have quite a number of instances of it running.

Have you gone with X3 yet Beepster? There's a de-esser in the Nomad Factory Blue Tubes package.

The VC-64 also has a very good de-esser in it.

Beep, try these:
 
http://www.digitalfishphones.com/main.php?item=2&subItem=5
 
They are very lightweight and actually do a fine job.
 
Spitfish is the one you want, but you might as well download the lot, as they are all free!

I made a preset for the sonitus multiband that has all the bands squished into the high range (except the lowest which stretches all the way across and I disabled) This gives me 4 bands of deessing for those really problematic vocalists.  The wonderful thing about it is that it does NOTHING unless there is a frequency spike in the region each band covers.  It covers "s", "sh", "t", gopher whistle, you name it.
It has become my go to de esser for sibilant vocalists (not for regular vocalists). 
It would probable also work well as a guitar mellower/warmer.
 
I tried to do the same thing with the LP multiband, but it LITERALLY fought me on it.
 
So far, the Nomad one seems decent.  
 
Also, I agree that the VC64 is not at all a resource hog.  Very efficient.  Using just the de esser should be almost no drag at all.

Spitfish was great - but 32-bit only - and its settings often do not save correctly in Sonar 64-bit versions.
Try the new SPL de-esser plug-in; it costs $100, but it is VST-3 and 64-bit.
 
Works very well in Sonar.

You could also use a regular Sonitus comp with an EQd side chain input. That's basically what a de-esser is.