I can't cum on E either only had sex on it a few times gets frustrating after a couple of hours. For sex either no drugs or a glass or two of red wine is best IMO.
X can make sex even better but G is the bomb if you don't take to much. I could go for 3 hrs on G so it would always be the woman that would have to say ok she's had enough! I miss G!!!
You most definately can. All in all, I'd just consider something like "X" to be one of the vast array of mix-it-up tools that are out there. I'd put it right up there with costumes/roleplay, sharing erotic materials, and sex toys.
I have major problems getting it up on coke. Ecstacy is awesome for sex, as long as I don't take too much, then I get the same problem as coke. I used to sell ecstacy and needless to say have had my share of it over the years...will never touch that shit again. The day after x I feel like a retard and have actually had problems forming sentences...even simple ones like "hey, how you doing".
My personal favorite for sex is shrooms. They give you a wicked body buzz, tons of energy and a raging hard on. I can fuck all night on that shit and when I'm ready to quit I fall right asleep...no insomnia, restlessness or hangover what so ever. They're completely harmless. Only problem is I sometimes get sidetracked on stupid shit, like the carpet breathing or patterns forming on the bedspread. Or I get perma-grin and laugh hysterically at anything and everything.