I've never liked Theta CD players. To me, they sound very lifeless. I would definitely look at other players, as well. I had a 640V2 and thought it was very good for the money. Of the CD players you list, that would be my first choice.
That said, I would strongly recommend that you upgrade from your Pioneer first. I think doing that would make a much bigger difference than a new CD player. I would buy a CD player after you get a new amp.
That said, I would strongly recommend that you upgrade from your Pioneer first. I think doing that would make a much bigger difference than a new CD player. I would buy a CD player after you get a new amp.