Did your original stereo have 4 or eight speakers?
If it had 4 speakers, it is the base stereo and has no amp.
If it has eight speakers, it is the Midline system and has a 120 Watt 4 channel Amp.
If it has 9 speakers, it is the Infinity I system and has a 240 Watt 6 channel Amp.
If it has 11 speakers, then it is the Infinity II system and has a 320 Watt 9 channel Amp.
If it had 4 speakers, it is the base stereo and has no amp.
If it has eight speakers, it is the Midline system and has a 120 Watt 4 channel Amp.
If it has 9 speakers, it is the Infinity I system and has a 240 Watt 6 channel Amp.
If it has 11 speakers, then it is the Infinity II system and has a 320 Watt 9 channel Amp.