Hey man... Ok, some things to consider replacing on your Atomik...
The bars... some pro tapers will sort you out...
Tyres and tubes are rubbish, replace these when you can...
Forks - Get yourself some GPX Black Labels, the kit from DHZ is good as it comes with awesome GPX front brake setup too.
My throttle was rubbish... a Joker 1/4 or 1/8th turn throttle are good.....
If you want to upgrade the carb.... an OKO 26mm flatside is the go.... comes with the unifilter too usually...
Thats basically it... could replace the rear shock too, depending on what you do with the bike...