http://www.ebay.co.uk/itm/JBL-GT5-A3001E-MONO-1-channel-car-BASS-amp-amplifier-/250880434039?pt=UK_In_Car_Technology&hash=item3a69 a39f77

Perfect mono amp 175w rms @ 4ohms for €100 and matches sub.

Wasting yer money buying anything more. A headunit is more than capable of driving your spearkers as you most likely know already.