Yes and no!
Successful, Yes. New speakers, No.
2011 Doblo 263.
Removed the standard head unit and replaced it with a Pioneer unit with an active screen mount antenna.
Extra power feeds (using a piggy back fuse) to supply the antenna, and an always on supply to keep the radio memory alive. As an addition, I fitted a switched supply so I could listen to the radio with the engine/ignition off. This was fitted with a diode to stop any back feed.
The stick on antenna is unobtrusive next to the passenger side A pillar, and gives excellent reception - maintaining stations on where the factory fitted DAB in my other car dies.
The Pioneer doesn't over tax the standard speakers, and although I am no audiophile, its loud and clear enough to drown out Fiats wind, tyre and engine noise!