Well it all depends on how you set it up....
Are you using the RCA jacks from the back of the HU to the amp, or are you using the speaker leads...
Either way you are only goin to get 45W peak out of them either way you set it up, just whether or not how many speakers you can use is up to the setup....
if you use speaker leads then you can only use two or four speakers depending on if it is a 45x4 or a 45x2 amp...
If you use the RCA jacks then you can get an extra 2-4 speakers out of it depending on if its a 2x or 4x amp again...
