when u hook the amp ground wire to the frame does that act as the minus on the battery ?

 

yes as long as the battery - is grounded to the frame also

 

do u have to have a power wire with a fues or can u just use a plain wire ?

 

If it is the wire from the battery to the amp, then absolutly 100% have to have a fuse on that wire or you run a risk of melting the wire and possibly roasting your car.

The amp to chassis wire does not require a fuse

 

^ +1

 

does a amp that is 300max and 150rms and 14.4 volt strain the alternator
just as much as a amp that is 600max and 300rms and 14.4 volt ?

 

+10000000000000

 

A=(W/V)

(150/14.4)=10.4 < (300/14.4)=20.8

The 150 watt amp will draw 10.4 amps off of your alty, and the 300 one will draw roughly more depending on the efficiency of the amp.