If you do not want them in the rear deck then that leaves the rear side panels, the doors, possibly the kick panels, under the dash, under the seats, or in the factory indash location. The choice is yours to where you want them. If you do not want to modify the factory side panels, kick panels or the doors like you do not want to modify the rear deck then this will leave underdash, underseat, or the factory dash location. Speakers underdash or underseat will need enclosures around them while ones in the dash will need to be installed in an infinite baffle style or also have an enclsure around them too. The higher the frequency the more directional the speaker becomes. If you want to hear the cymbals and upper frequencies you need to be able to see the speakers or have them reflect off of a hard surface like the back glass or windshield. Speakers under the dash pointed downward or speakers under the seat pointed forward will allow your ankles to possibly hear the high frequencies but they have a harder time reaching your ears while you are sitting in the car's seats.
You can install speakers in a stealth type of installation however you will not be able to mount the speakers and have sound come through the factory vinyls. The speaker must be allowed to have the sound flow unimpeded through it's grill or covering.
What do you want to see or not want to see or what could be covered in different material to suite your needs and wants ?.
Jim