I'm with F&B on this, for the most part... when I'm on a psychedelic, the very last thing on my mind is sex. In fact, most psychedelics (and stimulants) make it virtually impossible to have sex even if I want to. There are a few exceptions, but even on those substances I don't have an increased urge for sex, I just retain the ability and experience some enhancement sometimes.
5-MeO-MiPT - This one is great for the erotic. Very mentally and physically stimulating.
2C-T-21 - Also great, more physical and less mental than moxy.
LSD - On a not-too-high dose, it can be very fun. Still, the desire is lessened unless the situation presents itself.
Also, there is no fucking way I could have sex on MDMA. Even when it worked for me, I felt intense love, but it was very non-sexual. In fact, the thought of sex while on MDMA seems unappealing. Not to mention, like all amphetamine-type drugs, it makes it very difficult if not impossible to get it up, and even if I manage it, it will never end due to numbness.
I also agree that cannabis is wonderful for enhancing the erotic. That one definitely is usually used because it works so well.