Best tubes for Audio Note Cobra Integrated

Looking for some recommendation to replace stock tubes in AN Cobra. I am getting a used Cobra soon and being a tube roller quite often just need a little direction for other tubes you guys are using in Cobra. I assume 4 power tubes would be the fist in line to replace to get different sound. Will other 4 small tubes have also significant effect on sound when replaced? I realize that AN tuned this Cobra to sound best with the stock tubes but every system is different and tube rolling can achieve much better results. Your advice is very appreciated.