Hmm. From a purely hedonistic standpoint, opis+benzos feel GREAT but as has been mentioned many times, it is a dangerous combo that has killed many so it should not be attempted by anyone ever...
That being said. These days I'm a big fan of kratom+etizolam+gabapentin+weed. Just pure bliss. But if you mix downers please be sure that you know what you're doing. I have had some wonderful experiences on heroin/oxy mixed with Xanax/clonazepam, but I have also done that combo and woken up in the hospital. I have also seen one of my closest friends die right in front of my eyes, if we hadn't given her the narcan we would have lost her....please be careful out there.
Back when I had a girlfriend, my favorite combo of all time was Adderall+heroin+weed+sex. But now sex isn't something that I come by too often, haha. Also, FWIW, I have had peak experiences on psychedelics that have left me with a bliss far more profoundly impacting than anything that any opiate or benzo has given me. The euphoria after peaking on DMT is just unreal. Same with MXE. I'm sure if you're a real hardhead you could mix the two but I'm just not that crazy.