If you don't intend to get an amplifier then you should get yourself a 3 way 6"x9" speaker(at the rear) for better bass. I presume your HU is rated at 50w x 4. This is max power so your nominal power(RMS) rating should be approx. 20-25w RMS. Look for speakers that have a rating close to the HU RMS power and not maximum power, otherwise you will underpower your speakers too much. This will not only spoil the speakers but will not sound good also. I believe the 'Brothers' speakers was underpowered, that is why it sounds lousy to you. The demo was done with an amp that's the reason you find it nice when you bought the speakers that time.
It is hard to get good speakers at 20-25w RMS but try to do some audition first asking them to install at your car then you will get the true picture. Sony, Kenwood, Pioneer produce good speakers attractive to the mass market (value for money) whereas some European brands like Focal, DLS, RS, Dyna Audio, MB Quart, Eton etc are more for audiophiles which could cost a bomb. Remember, when you get speakers that have much higher power rating than your HU will cause your HU to work harder because it needs to pump up to max. power to make the speakers work. This will eventually, shorten the life of your HU or speakers as they go into distortion faster when you turn up the volume to compensate for the low power. :shades_smile:
