Start with the room, not the spec sheet

The single biggest influence on how an amplifier will behave in your home is the space you're putting it in. Most of us are working with a British living room: perhaps 3.5m by 4.5m, a bay window, a chimney breast, and a suspended wooden floor that behaves like a drum at 60Hz. Rooms like that reinforce bass, so you need far less power than the figures on the box might suggest. An open-plan kitchen-diner with hard floors and a vaulted ceiling is the opposite problem — the sound has nowhere to hide and the amplifier has to work much harder.

It's also worth being honest about how loudly you actually listen. Most people settle at an average of 75–80dB — conversation level to busy restaurant — with peaks of 100dB or more on a drum transient or a full orchestra. An amplifier has to deliver those peaks cleanly and instantly. That's what headroom means, and it matters more than a 10-watt difference in the headline figure.

Match power to speaker sensitivity first

Speaker sensitivity is quoted in decibels per watt per metre (dB/W/m), and it tells you how much sound you get for each watt. A typical small standmount might manage 86dB; a big floorstander with multiple drivers could be 90dB or more; some sealed or studio-style designs dip to 84dB. Every 3dB is a doubling of power, so a 84dB speaker needs four times the watts of a 90dB one for the same volume. As a rough starting point:

• Small room, up to 15m², speakers rated 88dB or higher: 25–50W per channel is plenty.
• Medium room, 15–25m², speakers around 86–88dB: 50–80W per channel.
• Large or open-plan space, or speakers below 86dB: 80–150W per channel, with a good power supply behind it.

Impedance matters as much as watts. A speaker sold as "8 ohm" may dip to 4 ohm or lower in the bass, and that's where cheap amplifiers run out of puff. Look for an amplifier with a genuine 4 ohm rating, and be sceptical of any that simply doubles its price with its power claim. Current delivery, transformer size and reservoir capacitance tell you more about grunt than a single number.

Count your inputs before your watts

An amplifier you can't connect everything to is no bargain. Before you audition anything, write down what you own now and what you might own in three years.

• Analogue line inputs: three is comfortable, two is workable, one is a compromise if you have a CD player and a streamer.
• Phono stage: if you play vinyl, a built-in moving magnet stage saves you £100–£250 on a separate box and one more pair of cables. Check the gain — moving magnet stages run around 40dB, moving coil needs closer to 60dB and often a step-up transformer.
• Digital inputs: optical and coaxial for a television or games console, USB for a computer, and HDMI ARC if the amplifier will double as your telly's sound system.
• Streaming and Bluetooth: handy for casual listening, but a wired network connection or a decent separate streamer will usually sound better.
• Pre-outs and a subwoofer output: the single most useful upgrade path you can buy.

Living with it day to day

Two amplifiers with identical specifications can feel completely different in use. A well-judged volume control gives you fine adjustment at low levels rather than jumping from inaudible to too loud in a quarter turn — crucial if you live in a flat or a terraced house. A decent headphone output is worth as much as an extra input to anyone who listens after ten in the evening.

Think about heat and power too. Class AB designs run warm and want breathing space; Class D runs cool and efficient and is now genuinely competitive at every price. Valve amplifiers need ventilation, a few minutes to warm up, and a little more care. Check the standby consumption, and whether the amp remembers its input and volume when you switch back on. Small things, but you'll notice them every day.

Audition at home if you possibly can

Shop demonstrations are useful for narrowing a shortlist, but your room is the final arbiter. Ask to take a couple of contenders home, or at least buy from a dealer with a sensible returns policy. Take your own speakers and your own music — a favourite recording you know intimately will tell you more in thirty seconds than an hour of unfamiliar demonstration tracks.

Listen for hiss from the tweeter with no music playing, hum from the phono input with the volume up, and how gracefully it behaves at quiet levels. Then listen for whether it holds instruments apart when the music gets busy, and whether the bass stays tidy or turns into a single thud.

Planning your upgrade path

A good integrated amplifier should last a decade or more, so leave yourself room to grow. Pre-outs let you add a power amplifier later. A fixed line-level output lets you feed a headphone amplifier or a recording device. A spare shelf and a spare mains socket will save you a headache when you inevitably add a streamer or a DAC.

On budget, resist spending everything on the amplifier. Speakers make the largest difference to what you hear, and a modest amplifier driving excellent speakers will comfortably outperform the reverse. Spend sensibly on the amp, generously on the speakers, and put the rest aside for decent stands, some speaker cable terminated with 4mm banana plugs, and a rug. Your room will thank you.