Unless you have extremely nice and expensive speakers/subs, then you won't really be able to tell a difference with SQ either way. If you are planning on only getting coaxial speakers, then just buy a weak amp, and use the speaker level input wiring harness that comes with the amp, and tap into the speaker wiring behind your deck, or near your speaker mounts, it will work fine. You can even use the same process to tap into your rear speaker wires for the sub amp, and just use the low-pass crossover. Again, unless you are getting some very nice component speakers, and have much experience and are VERY picky, then the normal ear cannot tell a difference.