Sony Needs Replaced

Got a cheap sony head unit as a present a year and half ago and it seems to have died. The unit keeps switching its self on and off.

When it switches itself off I can here the amp clippping as its cheap (think its been damaged as i drive around with my tunes as loud as possible before the speakers distrort), I dont think its worth fixing.

My questions is it worth buying a medium range unit, even though Im using the speakers fitted by the car manufacturer.

If I will find no improvement as Im suspecting as the speakers are buckshee, whats the reccomendations for a budget unit at a good price (model and where to get best deals) that will last better than the Sony. Had a cheap Blupunk and it never let me done in 5 years of heavy use.

My cars a Mk3 Golf Gti with 8 VW speakers as standard (any adice from someone with same car would be very much appreciated).