Film Photography Podcast store has a lot of Industrial Ektachrome in 35mm available, in 320 and 160 speeds. It was deep cold stored, has lost little if any speed, and the colors are amazing. A bit more muted than Fujichrome 400, in my opinion. I'm buying enough to last a few year/summers of shooting.
Where do you have your E-6 done? I have been using Dale Labs (www.dalelabs.com) when I want a scans because they offer amazing scans at the time of processing and and Dwyane's Photo when I don't need a disc. I also use Praus Productions for 4X5 only. I have kept it all Kodak. They all use Kodak chemicals. Praus is a Q-Lab.