You may have seen my posts over the past couple of months regarding my situation regarding this setup. (It is exactly the same as you have now) Anyway, I have been running my kappa with roughly 150 watts at 8 Ohm and it does a nice job. However, it is no where near enough for the sub. You will have enough low end to occasionally rattle a door or something loose, but only when watching Transformers or something. (And not all that often) But, it does sound really nice, and integrates very nicely with music, depending on your mains.
You will be OK with the OAudio, but in no time flat you will be wanting more...believe me!