Hi and welcome to the forum.
Some poeople describe darjeelings as astringent, so it may not be what you want. Ceylon is rather mild, too mild in my opinion, as it often suffers from a general lack of flavore--but there are some good ones out there. So they say.
My rec's: Adagio's Yunnan Gold (or any other yunnan black like it, but Adagio does have the best price). A yunnan black, also called dian hong, with a high percentage of khaki buds--the more buds, the more smooth-is wonderful, smooth, and unlike any other black tea.
I just had some of this last night, too, and I thought it was very smooth: http://www.tfactor.us/catalog/limited-edition/koucha-706.html
Its a Japanese black tea.