First should be budget. How much do you want to spend? Other important factors are sound quality, speaker size (do you want a 6x9 speaker, a 6.5-inch speaker or something with a killer bass?), as well as design. To help you make the right decision, we only choose the highest quality speaker such as Gravity for you to buy. Here is a very well put together 6x9 inch car coaxial speaker from a great electronics company. It includes mid-bass, tweeter to produce a very good sound quality. It's hard to see anyone disappointed with this 6x9 inch car coaxial speaker for the price they pay for it. This speaker is rated for 300 watt RMS power and 1000-watt peak power. That is plenty of power for it to produce some nice high, mid-level and even lower bass sounds. Technical Details: AB-690 6"x9" 4-way speaker set At least 700 Watts per speaker Max. Input Power: 1400W / 2 speakers Voice Coil: 25mm Sensitivity: 90 dB Magnet: 10 Oz Impedance: 4 Ohms Frequency response: 45 - 20,000 Hz Injection Cone Woofer MidRange & tweeter: 35mm (1.38in) Mylar Dome Tweeter: Piezo tweeter AB-630 Size: 6.5" Type: 4 Way Coaxial Car Speakers Power Handling: 400 watts Frequency Response: 65 - 20000 Hz Sensitivity: 89 dB Voice coil: 25 mm Magnet: 10 Oz Midrange: 30 mm Mylar dome Tweeter: 2x15 Piezo tweeter Package Contents: 2x AB-690 Speakers 2x AB-630 Speakers