I agree with the points Stanz and Duanes made. You may have more trouble than it is worth trying to get your texas to accept a community.
I would say though, that you haven't given it a "correct" try. Two adult cichlids is never going to work; one will be dominant and the subdominant one will be bullied to death, because the dominant one sees the tank as his territory. And there is nothing else to distract him from the subdominant one, so the bullying is relentless.
If you wanted to try again to add cichlids with him in the 150, I would get no less than three, and make sure none of them look similar to the texas. Salvini, convict, and jack Dempsey for example. I would get the three cichlids all around 3", so the texas does not feel his dominance is challenged. I would add some large swordtails/mollies/etc at the same time as well. The hope is that the texas would accept the group of smaller fish as subordinates, and even if he does bully them, he will be distracted in three different directions, so nobody will get it too bad. I would also re-arrange the entire décor as much as you can, to hopefully confuse the texas into thinking it is no longer his tank. I would also keep a divider on hand, with cichlids there are no guaruntees and this could all still not work.
Another option would be to get a female for him and a school of livebearers; much easier to do and would be nice