To convey a similar *feeling* depending on the context, you might use phrases like:
* Mega: (Mega-) This means "mega" and is a common way to express something being extremely good or impressive. "Mega geil" (mega cool) would be closer in tone.
* Wahnsinn: (Madness) This implies something incredibly impressive or amazing.
* Genial: (Genial) This means brilliant or genius, suggesting excellence.
* Hammer: (Hammer) This literally means "hammer," but colloquially means something awesome or fantastic. "Das ist 'n Hammer!" (That's a hammer!)
* Obergeil: (Super cool) This is a very informal and emphatic way to say something is extremely cool.
The best choice depends entirely on the context in which you'd use "like a G6." If you can provide more information about the situation, I can give you a more precise translation.