I've got a Sattelite and considered upgrading, but I came to the conclusion that the Reynolds frame wasn't worth the upgrade. For the money you'd spend upgrading you can probably buy a new 105 equipped bike.

The Sora group is fine. They might not be racing quality components, but they work fine. People's main issue with them seems to be that they have thumb shifters rather than sti shifters.

Actually I think the group & frame are a good fit. I use the Satellite for commuting/touring so it's a good match in my opinion. The frame is heavy and has alot of flex, so I can't really see the benefit in upgrading components.