Component speakers or as you called them splits sound great up front as long as you position them correctly. Depends what you want from your system, also depends on your head unit capabilities as well, the car maker just put a matching kit into the car if you using a original head unit with bigger wattage speakers it wont put out the sound your after, adding a amp to drive them is the only way to get the best sound out of them.
If you want a bit more bass without using a sub just run 6x9 in the back by removing the plates from the back shelf, just your fist will knock them out , cancel the back door speakers and run the 6x9 from a amp.
Those active subs that fit under the seats are good, pioneer or kicker brand will give you a buzz... I learnt to keep it simple, your ears are very important tool and do adjust to sound, I started off with 6x9, then went up to 10" sub, then 12" sub, as you condition your ears to that sound you just want more and more which means going bigger, then I was told that's due to your hearing getting damaged and your becoming tone deaf.
My advice keep it simple with a good balance all round sound.