If going 455,I would buy the American. I own a few 452's and 453's. Reports on Rimfirecentral are that the 455 may be slightly less accurate than the 452 or 453 but it could also be within the margin of error for individual guns.

I think you would be hard pressed to buy a better rimfire for less than $1200.

The 455 has the benefit of being able to use a Lilja aftermarket barrel which have been reported to shoot very close to a 54 action Anschutz. Lots of money though if you add a Lilja but you could always get one later and it wouldn't be too bad.

Personally,I would shop the classifieds at www.rimfirecentral.com or ask around on the CZ forum there and try to pick up a 452 or better yet 453 American.