Last night I wired up my AU265s as fronts (where they have been for a few months now) and the UP1203s as surrounds. I rented the Criterion edition of The Rock. I'm not going to say it's a good movie, because it isn't. It is, however, an excellent version of a loud film that throws noises around all 5 surround channels. As a bonus, the Creterion disk has DTS soundtrack which sounds significantly better than the Dolby Digital version.
Using 265s as fronts and 1203s as mains presents a couple problems. First, the 265s are 4 ohms and the 1203s are 8. This meant that the fronts were significantly louder than the rears, and tended to drown them out. I turned up the surround channels by a 7 or so dB on my pre/processor, but only did that after watching The Rock. I've got Tim Burton's 9 out as well, and I'm going to watch that with the channels adjusted. I should add that my center channel is also 8 ohms, but it didn't seem to be overpowered by the 265s at all. Another issue is that the 1203s have 12" woofers, and go much lower than the 265s. In spite of the difference in levels, I did notice a lot more bass coming from the back of the room. I suspect I can mitigate this with a subwoofer purchase.