I have the chico keyfit carseat/travel system AND I have a sit'n'stand stroller (although mine is the Babytrend brand). I'm assuming you have an older child if you have a sit'n'stand? We had the travel system with our first daughter and it was great. A bit bulky, but a great system. 3 years later we had another baby and got the sit'n'stand. It works with the carseat very well.
I think you need to figure out how much you will use a stroller with just the baby, or if you'll need it for your older child also. I hardly ever use the travel system any more because I always have my 3 year old with me so I use the sit'n'stand.
And I agree with what everyone else has said, go to BabiesRUs or BuyBuy Baby and find out if the chico fits with the F.P. stroller.