It probably is too late, but for those of you reading this it may help in your own decision.
I personally feel that de-clawing is inhumane and an easy way out for pet owners.
With a little persistance on your part you can train your cat, whether it be Siamese or something else, to use a scratching post. Cats are very smart, especially Siamese, and they will learn quickly.
I have grown up with Siamese cats and all of them used a scratching post and never destroyed any piece of furniture.
You show them the scratching post, and even show them how to scratch. Then, when they try to scratch your couch, say no, take them to the scratching post and tell them how good they are. By doing this a few times they will learn and eventually leave your furniture alone. Some people will even use a spray bottle of water to help their cats learn what the word no means.
Trust me, by doing this you will save your furniture and teach your cats what the word no means.
And both you and your cat will appreciate it!

I kinda forgot that I posted this thread...but I decided not to declaw my siamese Cat. If you want to know he is a Seal Point and his name is 'Sushi.' He is about 14 months and I love him to death!