No, a pre-amp line driver definitely won't help. RCA/3.5mm is all line level, speakers are... speaker level.
Voltage on a line level can be from 0-15 volts depending on the volume and the capability of the device putting out the sound. A line driver might be able to boost line level volts from a low voltage source at like 3 volts to 15 volts, but it doesn't convert from line to speaker level.
What you could do...
- get a head unit with aux in and speaker level out
- get an amplifier and feed it the RCA and have it feed the speakers
- get an amplifier and feed it the RCA and have it feed the stock amp