my profession used to be this subject, so I know all about it. In my opinion, the best, well known components are as follows, from my experiences with personal equipment, and the stories I hear from customers:
Head units: Pioneer. Hands down, I will never buy any head unit other than pioneer. the radio tuner is far better than other brands, the actual RMS power is usually higher than other brands because of the MOSFET power supply(Metal Oxide Semiconductor Field Effect Transistor- switches faster than other power supplies, thus creating more power with less heat), And the user interface is generally much easier to get used to than other brands.
Amplifiers. I am torn here. For high power systems, I prefer JBL amps. they overheat less than other amps, and they are rated at their actual wattage, not theoretical wattage like other brands do. Plus the power is clean and consistent.
For lesser powered systems, I have have had a lot of success with Kenwood amps. these will probably be the amps for you to use. Keep an eye on their RMS wattage, and pick subs up for them accordingly. for rock music, a good single 12" should do the trick. Also, see if the amp is one channel or two, and see if the channels are bridge-able for use with one sub. Another thing to look for is the resistance the sub is capable of. Usually, with lesser powered two- channel amps, they are capable of 4 ohms when bridged, or 2 ohms when the channels are used separately. if you are using a 2 ohm resistance when bridged, you will eventually kill your amp. Lighning audio sucks. those amps don't look bad, but they are built badly. I have found with cheap amps like profile, jensen, or lighning audio, those amps die after a year or so, cause the capacitors leak, which is never good
Subs. The brands that you can't go wrong with are pioneer, pioneer premier, MTX, eclipse, pheonix gold, infinity, and some others that slip my mind at the moment. Make sure the wattage either matches the RMS power output of your amp, or can handle up to 50% more power than the RMS of the Amp. In your case, I'd recommend a single 12" sub, mated to a bridged 2 channel amp in 4 ohms. by getting a 2 channel amp, you open up your options for upgrading later for less money.
by getting subs and an amp to push the bass, then you alleviate a lot of power consumption from the deck. you can usually turn down the bass to the regular speakers, and only push midrange and treble with them. by doing that, you can turn up the volume a lot louder. if they start to destort, turn down the volume. even if the speakers were capable of say 150 watts rms each, but you deck only pushes 25 watts, and the speaker start to destort(clipping), you can kill your speakers. Contrary to what a lot of people think, it's not a lot of power that kills speakers, it's heat. Heat builds up when speakers can't move along the full sine wave, and distort.
One last thing- don't cheap out with small cables for your amplified system. you are only robbing yourself if the wires are the bottleneck for the power.
