I hate ordering from Satellite. The process is so slow and it'll be two weeks till you get your shit if you lucky - their fill rate hasn't been to great for me either. I'll order several things and never know what I'll get till it comes. Even then, they've fucked up orders for me.
Dancetracks is pretty straight forward, pretty good fill rate too. If they don't have it in stock, you'll know before you place the order.
Planet X has to be my favorite - selection, price, process, fill rate.
Haven't tried Vinylmania.