What kind of issues are you having with HD/Native? I spent 3 years tracking full bands with HDN in an old-ish HP z820 tower(dual 6-core XEONs @3.5GHz and 64GB of RAM). Up to 32 live inputs, 6 stereo headphone sends, several dozen plugins at a 64 buffer. I agree with Darryl that system problems are not likely to go away and you should work to solve the issues before you drop a few grand on the HDX card.
First step; Post a Sandra report on the computer (
https://sisoft-sandra-lite.en.softonic.com/)