Out of all the options I’ve seen here, and the budget you specified, I can tell you that your very best option that will give you the most notable improvement in sound quality would be buying the EP600. The sub alone will astound you and even though it isn’t a sealed sub, it is incredibly musical. The 500 is good, but the 600 is great. I upgraded to the 600 from the 500 and have absolutely no regrets. Get that first and then contemplate an additional amp.