I put the GX302s in my truck in combination with CDT CL-69S.2 in all 4 doors. I think the 2-ohm 3.5s are getting too much power in comparison to the door speakers in this combination, since they are wired in parallel. There is almost no bass from the 6x9s and the highs from the dash are overly harsh. It required me to up the bass on the EQ to near max and cut the mids and highs downwards to get it to reasonable sound quality, but I'm still not happy with the combination even after the adjustments. I'm planning on swapping out the JBL 3.5s to a 4-ohm set and see how that works.
I know many on this forum like the GX302s, but many of them have the Apline system. This makes sense because the stock dash speakers are 2-ohm in that combo vs. 8-ohm in the base system and they have additional processing/crossovers/amplifiers to address that. However, for the base system I don't think they are a good option. They are a definite improvement in quality, it just is not a good balance when mixed with the rest of the system.