the berth you plan to sleep in is a no brainer. do it now. we waited 6 months to address it and now rue every night we didn't have our froli and new foam.
The mattress we got from over stock.com, the serta 4" (3" firm, 1" memory) for around 100 bucks. We got a king size and cut it down with the electric knife. Cover it with mattress pads and then sheets. when ever you get all the cushions replaced you can have the mattress covered to match if you wish.
The froli is worth every penny. Its a spring system for under the foam mattress.
it makes ALL the difference in the world having a comfy bed!
ain't what ya do, it's the way that ya do it...