you need an amp with about 150watts RMS @ 4ohms and is also CEA-compliant
when it comes to car audio nine times out of ten you get what you pay for- and you need to look for CEA-compliant brands which means that the amps have been tested and produce or exceed the advertised RMS wattage with minimum distortion (distortion is the main cause of speaker damage over time)
here are the top CEA-compliant brands
Alpine
Bazooka
Blaupunkt
Clarion
Eclipse
Infinity
JBL
JL Audio
JVC
Kenwood
Kicker
Lightning Audio
MTX
Pioneer
Polk Audio
PPI
Rockford Fosgate
Sony
my recommendations
http://www.sonicelectronix.com/item_12250_JBL+GT5-A3001.html ($130 175watts RMS)
http://www.sonicelectronix.com/item_7561_Orion+HCCA-D600.html ($250 perfect match)
http://www.sonicelectronix.com/item_9852_Rockford+Fosgate+Punch+P300-1.html ($165 perfect match)
http://www.sonicelectronix.com/item_6750_Kicker+ZX300.1.html ($135 perfect match- my choice)