Can anyone tell me if chocolate rum moose and grand meriner moose would taste o.k. for fillings in the same tier of chocolate cake??

I'm not a chocolate person so to my palate, no.

I would recommend that you put it together with some scraps, (or make a couple of cupcakes) and taste it for yourself. That way you will get a small taste of what it would be like all together.

Either would taste great though I'd prefer the Grand Marnier.

Either mousse will taste good, but I don't know that I'd put them in the same tier. I like grand marnier but I'm not a fan of rum so to me putting the two flavours, with chocolat in the same bite doesn't sound appealing to me. You would have to make them and test your flavour combinations to know for sure.

Grand Marnier mousse will go great with the chocolate cake. I'm not so sure about chocolate rum in the same tier. Somehow when I think of rum, I think of coconut, and pineapple, and other combinations.

The Grand Marnier with chocolate is a classic, like oranges and chocolate.