I had a G-Force for a little while, but a different model.
My opinion – the low prices reflect the quality – I honestly wouldn’t recommend them for kart racing, or any motorsport other than autocross or real slow drag racing. I’d never wear one in wheel-to-wheel competition again.
The problem I had was that the padding inside seems “too” soft – I’m guessing it’s probably a very cheap, low density foam material. What fit well when I bought it, quickly got compressed through (minimal) use to the point that the thing was loose enough that I didn’t feel safe in the event that I might go upside down.
If you want a better quality helmet from that website list in that lower price range, I’d look at the HJC AR-10. I got one from Ted Hamilton (you can probably pm him – he’ll definitely help you out). It’s still on the heavier side, compared to the mid-higher end Arai, Bell, etc., but the price is a lot lower, while still retaining good quality and fit.