I checked all the polarity, it was correct.

That is really odd At first I thought that your box might be to big for the subs but then they will perform at a different ohm configurations... Have you tried testing them separate. There might be something wrong with one sub and not the other.

I feel no excess heat at 1 ohm. It barely gets warm at all from what I can tell, after a 10 or 15 minute ride.