then my fronts can the amp be adjusted so i dont blow them?

Im new to car audio but want to build a decent sounding system. Im looking at buying a 6 channel amp. Its a JBL gto755.6II with 60x4 rms and something like 107 watts rms bridged for the sub. I will be doing the install so i thought having one amp would simplify that.

The front speakers are 4x6 JBL GTOs with 40 watts rms. The rears are JBL 6x9s with 100 watts rms. Can i use this amp and adjust it so it doesnt blow the fronts. IM going to use some bass blockers on the 4x6s around 600hz.

The head unit is a pioneer DEH-P47DH 1.5 din. I want to add some bass to it later with a single 10" sub.

Do you guys think this will sound decent?

 

Usually a speaker starts to sound bad long before it reaches its max rating.
So one answer to your question is that you can use your ears to decide when to stop increasing the volume. You will be almost unable to perceive the sound level difference between 40 and 60 W but the distortion will increase dramatically above say 20 W. Damage protection of a speaker is a complex issue that is not easily resolved with any devices I know of. Besides, a 40 W amp is actually capable of damaging an 80 W speaker, in particular it's mid and tweeter units (which might be 10 and 4 W units).. Most of the power in music is below 600Hz so the 4x6's should be safe anyway, so I'd go ahead with that amp. Just keep the sound of it clean and you'll be in the green..