without over analyzing or overthinking a possible cause, for sure its an easy test to set your ASIO buffer size to 256 or 512 samples to see if it goes away.. I don't know many systems with rock solid performance across the board at 32 samples.

If you increase your sample buffer to the maximum, does the distortion go away?

If i know what synths you are using i can run some checks and see if i can replicate the problem. More info=better and faster solutions.

ISSUE RESOLVED!  Thanks to everyone for all the suggestions.  
 
I changed buffer size to 128 samples and the distortion was much worse.  I changed to 512 samples and it disappeared.  The cost is a tad more latency than I want.  But I hope some fine tuning can reduce that or learn to live with it
 
Many thanks again for all the suggestions.  

Are you sure you're running the latest drivers for your card? 32 samples giving you 45msec of latency at 44.1KHz should be an impossible combination of figures no matter what else is going on. And 512 samples seems a bit excessive for a decently specced system like yours.

Also, what was your buffer latency set to in MixControl--short, medium or long? If short, then that will seriously tax your CPU.

And could you please clarify what you meant by "external VST?"