i think the most noticeable upgrades are saddle and tires (admittedly i don't run sexy skinny high pressure tires anymore because i'm looking for better wear now for sick wicked sweet skids, or moreso flat protection. but kevlar bead 145psi tires will definitely feel faster and more responsive)

next is foot retention. consider pedals too since the stock ones feel like the bearings come pre-destroyed. at least get those exustar laminated doubles. I've never used them, i've only used mks or toshi doubles, but they look similar enough to use. I'd really recommend getting into clipless. mountain style shoes and pedals are pretty forgiving off the bike. but clipless isn't well liked by many here. those that have tried it love it though. then a stem that fits you.

wheelset is good enough, cranks and bb are not glamorous, but good enough. handlebars are handlebars. the brake hoods are uncomfortable, i'd got with R200s if you're gonna keep them.