Blues are what Joe includes with his AC20's with the option to upgrade to a Gold. These are the only 2 speakers I've tried with the AC20 Deluxe, you can't really go wrong with either, although I prefer the Gold.
Blues sound fantastic with it, as well as the Gold. The blue sound more raw, the gold more refined with less speaker breakup. For controlling volume, a G12M20 heritage can be used. Still very nice sounding and 96db
Would also like to note that the Weber Alnico Blue Dog 15w) is a great option as well. To my ears closer to the original vox silverbells (late 60's) - slightly more rounded on the top end and less efficient than the modern blue alnico. If you want something between a blue and a gold the 30 watt weber alinico is a great speakers as well. The weber silver is a bit too dark for this amp, which is based on the normal channel of the ac30 (or ac30/4 ef86)