It replaced a Soloist 1.
I have not heard the Aria Int.
Asked the dealer the same question and his reply was:
"The Aria Signature is really nice. Clearly more powerful than the Aria it takes wonderful control of the bass and just opens up the soundstage. There are really many ways the Signature excels over the Aria."
I have heard that new Arias are on a 6-8 week back-order.
My Aria Sig has about 75 hours on it so far.
I like it a lot.