I use a GameCube to DualShock converter and use a PS2 controller. At some point I will get round to buying a wireless PS2 pad but I can make do for now.

I like the idea of a truly wireless Classic controller though.

I used to play IK+ a lot on my Amiga. Not sure if I would want to play the C64 version. I might give it a go though.

I use a PS2 Dual Shock controller through a GameCube controller adapter/converter. It works well for me and it was pretty cheap. The only other "retro" controller I would buy for the Wii would be a six button MD pad.