Sorry - I got my amps wrong, at least in your case. @240v they average between 1.8 - 2.3 amps. But I'm guessing you will be running it at 120v in which case it will pull roughly 5 amps. Incidentally Lumatek makes SWEET dual 600w ballast but you need a 220v line to run it. There are a number of versions of the 600w ballasts. Google these terms without the quotes "lumatek 600w dimmable ballast amps" and you will find your answer. Once you get the total number of amps required by your setup add 10% as a margin of error. And remember, a 20 amp wire is no use if the outlets are not rated for 20 amps. Well, not exactly correct. You can still carry 20 amps across the line but no more than 15 amps per 15 amp rated receptacle. So you can work around this by plugging in to multiple receptacles adding up to 20 amps total... All I'm saying is that if you plan to pull 20 amps out of a single receptacle then make sure it is rated to carry 20 amps.

You can run your amp question through wolframalpha.com with the terms "600 watts 120 volts" without the quotes and you'll get the answer or you can search for an online calculator.

Now that I've done your homework we can say with limited confidence that you should be fine with 35 amps between two circuits. I say limited b/c we don't know all the details of what else you plan to put on those circuits but you should be fine. Put your lights, fans, and other grow room plugins on the 20 amp line and the AC on the 15 amp line (check the amps needed obviously).