Dear Rui. I don't think we have K6 + GO curves for that printer as we came out with K6GO many generations after that printer stopped being sold by Epson.
I'm going to look back in my archives and see if we have any curves made up for either 76 or 22 (same print-head) on that paper. We are working on re-organizing our curves library so rest assured, finding all of our available curves (and master curves) will be easier soon.
Your 9600 should be used as your GO printer. It's MUCH MUCH better than the 7890 printers for GO printing. I don't suggest printing GO with any x890 or x900 wide format printer because of it's paper sensor issues and various ink starvation that happens when printing a single channel at anything other than 5 second delays between print-passes.
The other 9600 (with a few good channels) will work well with the GO and yes you can print multiple channels at a time. You just need a custom GO curve applied that we can build for you. (custom curve rate is $99). This would certainly up the dependability of the 9600 as a GO printer.