Added a Behringer UMC404HD interface, which I generally like. It got rid of all my audio latency problems.
But the MIDI ... ugh. Good 1/8th second monotonic, and worse poly.
Tried is against sever synths, including TTS, TruePianos and even drum kits.
Anyone fight this battle before? The one light on the UMC404HD makes me think the delay is not in hardware, but on the Sonar side.

Midi delay is often caused by plug ins and especially some that use "look ahead" processing like the LP Multiband. By Pass your effects while tracking midi. 
Another thing that hits my system is if the internet is on and something runs in the background. 

Are you using ASIO drivers?  This shows an overview of those settings:
 
https://www.youtube.com/watch?v=VE5i3oFIEW8