Clio 200 ff sat nav, with aftermarket headunit?

Looking to upgrade my sound system and I have read up a few things on here saying that the standard headunit can't cope much after installing decent new speakers all around, is this the case?

im no noob at ice but I'd like to keep all the oem controls and say nav options etc but just have an upgraded amplifier and speakers, is this possible with the sat nav
?

some one who has done this I'd like to know from you if at all possible.

Mail be using focal speakers as they are fantastic, krx3 if they fit.