There isn't a perfect ICS at the moment.. although there are some that are a lot better than the default (which is pretty, and quick, until you actually want to run some software, then it falls down)
Modaco.com seems to be the best forum for the G300, and there's a collection of roms overthere.
Infusion based on the official firmware, but with some tweaks, bug fixes and enhancements, is one of the big hitters. But doesn't have 3D hardware acceleration..
CM9 is based on the Cynaogen firmware, and this does have blazingly fast firmware, but ocasionally freezes when turning wifi on, and it doesn't have decent video playback.. you can work around this for local files by using MX player (from the play store) but iPlayer won't work on it for example.
After 3 days of running cm9, i'm really impressed and haven't hit any show-stoppers, or major slowdowns...
Have a look over there, and when you're ready (or considering how to go), have a look at the 'explained like you're five' sticky thread...