Since I personally feel the Crossfire qualifies as a "Sports Car", (not everybody agrees) then I think it's main competition would be just about any other "Sports Car" currently being built today.
An SRT6 with just a few mods can run with a Viper, and a perfectly stock NA Crossfire an go thru a slalom faster than a Ford GT.
So the lines are blurred.
But probably the closest competition would be a 350Z, Audi TT, Mazda RX8, S2000, Porsche Boxter/Cayman, and BMW Z4.
The great part is you can hang with all of these cars at a fraction of the cost.