Welcome! The “usual” tier upgrades in this range also include the following: HE4XX, HD58X, HD6XX, Sundara, Elegia, Elex, Ananda, and then beyond. If you already own the HE4XX, I could see it still being worthwhile to upgrade to the Elegia/Elex/Ananda rather than jumping all the way to the Aeolus/Clear.
See these current (smashing) deals:
Master of Puppets is an all time great album. Good luck.