I would NOT use any other amp other than the correct one, they are the same on al cossies, a WIM050, as fitted to alfa 164 2.0i turbo, ferrari 328, testarossa, fiat argenta 2.0i and turbo, regatta 1600, tipo 1.8 16v sport, 1.8 spi, uno turbo(cat models), escort/sierra cossie, lancia delta 1600ie, prisma 1600ie, thema 2000 turbo.
As said very cheap new, but also normally very reliable, maybe try one from a friends car ?
tabetha