Just get whatever coffee you like the smell of at the local Whole Foods and make a cold brew. It's going to give you 3x the caffeine per oz and not be bitter at all. After you make it, mix your new coffee base 1:1 with hot water and add sugar/cream to your liking.
To cold brew, just add 1.5 cups medium or find grind coffee to 8 cups of cold filtered water. Shake. Let sit for at least 11 hours in the fridge. Filter into container. Tada! An extremely low acid, non-bitter coffee base.