Hi Green92,
It really depends on how you think you're going to power your system. That is, if you're going to use the amplifier bypass or not. If you're not, then your concerns are important.
If you choose to bypass the amplifier, and do the bit of extra work, then you should get a powerful head unit to power the speakers.
If you choose not to bypass the amplifier, but instead choose to connect the head unit speaker outs into the harness so that your speaker out sound is going into your amplifier signal inputs, then you'll need to look more carefully.
There's peak watts and continuous/RMS wattage. You are concerned with RMS. Peak wattages can sometimes vary greatly compared to RMS, because there is no industry standard or regulation. For example, a powerful Pioneer deck my say 35x4 peak power watts, but really have about 15-18 RMS wattage. My head unit says 35x4, but it's really only a wimpy 7-12 watts RMS. Although most people hate having to a salesman for help, this is where you'll really need to ask about the RMS values if you're concerned with your power, and it's not listed on the display. The peak power listing isn't as important.
Higher signals that can be too much for your amp will shorten it's life span. Again, I have a wimpy radio, so connecting my radio speaker outputs to my amp hasn't given me any problems, and it gets loud enough for me. Maybe someone who has done the same thing, but with a more powerful RMS radio can give more input on what has been experienced as safe.
Good luck shopping!
