Amplifiers

Car amplifier: how to choose and buy well

Updated 20 October 2026

How many channels, and what are you connecting

First decide what you will amplify. A mono amp suits a subwoofer, and a 2-channel one suits a pair of speakers. A 4-channel amp drives front and rear speakers, and a 5-channel one gives four speaker channels and one for a subwoofer in a single case. So in your request say at once: front, rear or subwoofer.

Power and class

Look at power as RMS per channel and with the load impedance in mind, for example 4×80 W RMS at 4 ohms. You need some headroom, but don’t buy an amp far stronger than the speakers, because you can damage them. Class AB gives a warm sound but heats up and is bigger, while class D is more compact and efficient, so it is often put under a seat.

What to put in your request

• Number of channels — mono, 2, 4 or 5;
• Power — RMS per channel and the load impedance;
• What to connect — front, rear, subwoofer;
• Class — AB or D;
• Model or brand, if you have one in mind;
• Condition — new, or used and working;
• Wiring kit — needed or not, and the cable size, for example 4 AWG;
• Fitting and tuning;
• Delivery city and budget.

Example: “I need a 4-channel class D amplifier, 4×80 W RMS, for front speakers and a subwoofer, new or used in working order. With a 4 AWG wiring kit, fitting and tuning in Central, budget up to HK$1,100.”

What to look at when comparing offers

Offers can be compared only when the channels, RMS and impedance are the same. Ask whether the cables are in the price, because a kit with proper cable size and a fuse is a big part of the budget. Some amps have a built-in crossover and gain control, which makes tuning to the speakers easier.

For a used amp, check whether it has overheated, whether factory stickers are intact and whether the protection works. Listen to the amp on the spot if you can. New equipment usually has a warranty, but for a used one agree on it separately.

Common mistakes

The most frequent is to buy an amp without a wiring kit and then buy it later. The second is to forget that the car’s own electrics must carry the extra load: for powerful systems you sometimes need to strengthen the wiring and the battery terminal. The third is to save on tuning, because wrong gain makes the speakers sound harsh.

How it works on BlaBlaPrice

Create a request on BlaBlaPrice: car audio sellers reply with offers showing the price, what is in the kit and the timing. The platform shows the offer with the best value first, and seller reviews are seen next to it. Sellers see their place among the others and compete, so good terms appear more often. Contacts stay hidden until you choose an offer. Details are on the “How it works” page.

Match the amp with speakers and subwoofers and cables and fuses.