Hi David!
Shweet! Might as well go for the gold, as they say! 
Nitta san was a little uncertain about having an audio sample for kouki shamisen, as he said the audio quality will vary depending on the skin, and so couldn’t get a good representation.
The best audio example would be the shitan shamisen, because shitan shamisen and kouki shamisen both have karin dou. So it will sound quite similar to that.
I wanted to record it last year in Sapporo, but the only two kouki shamisen available was Nitta san’s (who’s shamisen has a larger-than-normal dou, and so will sound differently) and Kevin’s kouki shamisen, who’s skin is about two years old (and so will sound a bit duller than a shamisen with fresh skin), and so couldn’t get a good representation either. Doh!
Bachido member Chet bought a brand new shitan shamisen from the Bachido Store. I’m sure he’d be happy to tell you how he likes it. 
For a legit kouki shamisen, I would recommend getting a chuko (preowned) shamisen. As I’ve often said, shamisen are very expensive when brand new like a car, but once ‘driven off the lot’, becomes much cheaper. You can get a phenomenal shamisen for a fraction of it’s original price. And with fresh skin, it sounds just as good as a brand new shamisen. (because again, the skin affects the audio quality the most)
The K-02 shamisen is already called for, but the K-04 is really nice. Feel free to message me your budget, and I can pass it on to Nitta san. He would be able to find you other kouki shamisen to fit your budget.
Cheers!
Kyle