I thought that too initially... but classic army and G&P externals are orgasmic for ARs....
if you have an AK, look for KA and G&P externals. so on and so forth.
externals first, to make an AEG shoot accurately, you don't really need that much upgrades. Inner barrel, hop-up chamber and rubber, a good nozzle, and good air-seal are really it... For ROF or trigger response there is a bunch of other stuff... blah blah blah....
point is, leave the internals for now, buy the best externals you can to start off =D
you won't regret it.