It might just be me, but when it comes to overheads mic placement has more to do with an unbalanced sound than having a matched pair. Obviously if you're looking at the most balanced sound possible, you're going to want two mics of the same make and model, but if you can get the best possible stereo image that you can with proper mic placement, it wouldn't be absolutely crucial to have a matched pair in order to get a great drum recording. That said, if you have the money, picking up a matched pair of sdc's wouldn't be a terrible idea if you started getting serious about recording drums.