The Onkyo has HDMI passthrough, so yes, you'll need to run optical cable too for DD and DTS audio. It kinda looks like you may get DD and DTS over HDMI, in the Sony, but I can't swear to it. The site isn't real clear on that. But neither one will process the new HD audio formats found on Blu ray movies. To get that, you'll need to step up to the Onkyo HT-S908........
Onkyo HT-SP908 - 7.1-Channel Home Theater Package with iPodĀ® Dock | Model Information | Onkyo USA Home Theater Products
I don't see a Sony HTIB that does the HD audio.
I agree with Troy though. You'll be happier in the long run, if you get a good receiver that processes the HD audio formats, and get a good speaker package. It's going to cost a little more doing that, but it is so worth it.

Good luck!