God I miss my ion...
All I did to mine was a Redz bodykit (they look RUDE imo) and a flat Redz trigger, Freak Barrel kit and locking feedneck..... I reckon that's all you need.
I did put a QEV and TechT L7 bolt in but didn't really feel any benefit from them.
As Spangley mentioned above, do some subtle mods and start saving for a higher end marker. If you wanna stay loyal to Smartparts, get yourself a nice Shocker.