My opinion is (and has been for a while now) that the contents of the base is almost UNimportant. As long as it contains onions - the rest has little bearing on the final curry. Although, if it doesn't contain garlic/ginger they will have to go in at final cooking time.
To me, the curry is made at final cooking time. What goes in then(and it need'nt be very much) dictates your curry.
Many of course, will disagree - well this is just my humble opinion.