I put 4's in mine, sounds just fine.

 

What brand and model number?

 

all 4 are infinity's. The backs I got second hand off the forum, the fronts I got from crutchfield, forget the PN though. Whatever infinities are $40 or so.

 

Is there any way that I can test a CTM in a salvage yard before I buy it?

 

It could be done but you'd need power AND you'd need some sort of breakout box so you could trigger each function and check to see if the outputs respond appropriately, the headlights, wiper, washer, park lights, dome lights, door locks, etc.