Another upgrading thread.
I'm currently riding a 2009 Giant Avail 3, so it's got an 8spd cassette, and Sora derailleurs and shifters. I want to eventually upgrade everything to 105-level (as the cassette is SRAM and the crankset is FSA) components. I know I want to change out the cassette because while I like the spread of gears, I think my sweet spot is in a gear that doesn't exist on the 8spd. If I change the cassette, I know I need to change the shifters and the chain. On top of that, I also want a more comfortable ride. So what do I upgrade first, for comfort or for performance?