Did you have them de-clawed (obviously) and at what age? I have a Siamese that isn't too keen on having his nails clipped, I have to do this at least every 2 weeks, and I'm getting a little nervous that I may be into this for the next 20 years! I've heard that de-clawing is, well, inhumane....just looking for an easy out here 
As soon as I'd adopt one from the pound I'd schedule the declawing the same time they were going in for neuter/spay. A few of my adoptees already were fixed, so I'd just schedule the declawing. It costs more in the short term, since adoption fees aren't going to cover declawing, but in the long run it's saved my furniture and vet bills based on injuries sustained clawing one another while fighting. My cats still fight but can never manage to inflict much damage without front claws. Since they all live inside it doesn't matter that they can't cope with the outdoors.
Declawing has many, many critics, and I've actually had some "activists" get in my face at a party or other casual setting about how I'm torturing my cats. Yeah, as I always retort, I'm sure my kitties would've preferred I left them at the pound and perhaps gassed, as long as they kept their claws. Geez, I get that declawing isn't for everyone, but my kitties didn't feel much pain that I know of-nowadays you can pay the vet extra and keep them doped up for three days and by then they're perfectly recovered from any pain.
In the long run, I would think declawing your Siamese would be less traumatic than fighting over getting his nails clipped constantly.
As for the behavior of my cats, pre and post declawing, I didn't notice any difference in their basic personalities. Over the past 8 years since we started adopting cats I've had at least a dozen declawed...some have moved on to the Rainbow Bridge, but the seven running around here seem happy.