2003 Civic coupe install

as stated, 2003 Civic coupe, these things are tiny, trying to guess what length of RCAs is need. 25' seems too long and so does 20'. Anyone install stuff in one of these? i have the 4 gauge ofc for pwr and gnd already, remote turn on wire and the deck is coming very soon. Just trying to get an idea on length for other stuff and and headaches anyone has suffered in one of these, altho i cant imagine many in such a simple car