Re: HELP! The cat or the couch - one must go.
I didn't interpret it that way, it seemed to me that he was just trying to express the lengths to which they might go to save the couch, but I really didn't get the sense that getting rid of the cat was anything more than an attempt at humor in a somewhat stressful situation. (Though, like Fran I am quite glad he came to a cat lovers forum instead of a couch lovers forum!!)
As suggested, there are some things you could try, but getting a new couch honestly might be the better option.
If you want to try, getting the couch professionally cleaned probably won't do much, what it needs is a TOTAL cleaning in an enzymatic cleaner designed to get rid of pet urine. The only one I've had a chance to use is Nature's Miracle, and I got the "Just for Cats" variety.
It works great, but the problem is you REALLY have to soak any affected areas, in that the area soaked by the cleaner has to be larger (in this case, deeper) than the urine itself. It does sound like a lot of work to me, I guess you'll have to decide if the couch is work that amount of work.