question about running Steam on my Mac

so, I would really like to be able to play Half-Life and The Orange Box on my mac.

I do not really want to install Windows on my Mac via Bootcamp or Parallel Desktop or something... I've heard that you can play in Steam buying an application that's calledCrossOver Mac.

I would like to know if it runs very well, if you can play Half-Life or Portal perfectly on high detail with no inconveniences... Also I want to know how well it runs in online games, say CS Source or Team Fortress.

thanks.

bumps