yeah, stick with 4.1. 4.2 and 4.3 seem to be all ap garbage. though, mario kart should require a system menu before 4.0. if ur playing from discs, u may need to update the wiikey. I think the last update was 1.9s for galaxy. though, u might want to soft mod the system, so u don't have to waste discs.
edit: for galaxy, u can update from the disc. however, with the wiikey, u need to burn a wiikey update disc along with padding. the update is very small, so the wii won't read the disc normally (the reason for the added padding). however, soft modding will eliminate the need to update the modchip.