I personally like the Fall 04 lilac over the 03 or 06 lilac. Lilac is a pretty color either way. I was originally looking at it for my spring bag also. Couple things to keep in mind: get good pictures of the leather. Some of the lilacs did not distress well, in fact, it looks just outright awful, especially if you are buying from ebay. If you are buying from a boutique, make sure they have a good return/refund policy. As pretty as the color is, when the leather didn't take the dye well, it just detracts from the bag.
That said, good luck! I think the lilac with its grey hues goes well with so many different colors! Can't wait to see your pics once you get it!