The 95 and 96 models were only coupes, but 97 and on they started making sedans. So, the earliest model M3 with 4 doors is a 97. If I were you I would sell the civic and get an M3 you'll have a lot more fun driving an M3
But, since you want to keep this car for a while you should get what you really want, which sounds like the sedan. Just save up and in the end it'll all be worth it.