Best cushion for Taylor King queen sleeper sofa?

Because of the bedframe beneath the cushions, sleeper sofas are not as comfortable to sit on as regular sofas. I've sat on 3 Taylor King Kings Road sofas: one with Ultra Aire cushions, one with Spring Down cushions and one with Memory Down (which I didn't like). But it is very hard to find a TK sleeper sofa in stores to sit on. I'm guessing the cushions on a sleeper sofa would sit firmer than on a non sleeper sofa. Would Catalina Down cushions feel less firm and more comfy than the Ultra Aire or Spring down cushions?
Thanks, great forum!