Good Airsoft Project Gun?

Well, I currently own a Ares (Umerex) G36 and it is a pain to find external upgrades (and there is a lack of options) I want to save up for a decent base gun for my "project" I am currently thinking of a KWA KM4 or a Tokyo Marui M4 (If i find one) My price range is under 300$ and I am trying to avoid the CA M15a4 Carbine (almost everyone, including my dad, has one) I want to do something unique but with the option to upgrade (M4s are not unique but they are very easy to find upgrades for)