Any Intel Mac will do the job. I edit HD video on a 2 GHz 2Gb Mac
mini.
There is no "native" AVCHD editing on Apple software (iMovie, Final Cut Express, Final Cut Pro / Studio). Apple's editing applications "transcode" AVCHD using the Apple Intermediate Codec (AIC: only Final Cut Pro uses the Pro Res codec) which makes editing HD much less processor-intensive than editing native AVCHD on a PC.
For a list of supported camcorders for iMovie, for example, check here:
iMovie '09: Camcorder Support (actually, it lists the TG1, which is the US model number for the same camcorder).
Andrew.