Audio fidelity won't be amazing for ceiling speakers so spending on an expensive amp seems somewhat pointless.
Sound quality isn't great from poor quality or inadequate or badly fitted in-ceiling speakers, but that isn't true of all in-ceiling speakers. I have two quick stories that illustrate this...
I did an Hi-Fi and AV install job for the Chief Exec of a small group of hospitals. She is a Hi-Fi enthusiast and wanted some AV to match. She likes to cook and entertain so the kitchen is used a lot. I installed a pair of good quality in-ceilings just driven from Zone 2 of a Yamaha AV amp. A week or so later I was back onsite for some other work. A friend of hers was there too. She came over and said "I was surprised at how good the sound is in the kitchen. I wasn't expecting that." She is also a Hi-Fi enthusiast and has a £1000 Linn front end feeding a pair of Monitor Audio Silver RX2, so the bar was set pretty high.
The other story is from an install I did at a Doctor's house in South Manchester. I was part way through the cinema upgrade when he asked about some kind of streaming audio system for his property in Spain. I said I could give him a quick demo of a Sonos amp but I only had some in-ceiling speakers in the van so they'd just be propped up against a wall and wouldn't sound quite as good as box loudspeakers. I did the demo in his games room. The guy looked visibly shocked. In that room he had a £1500 Bose lifestyle system. A £250 pair of in-ceiling speakers had just blown it away.
Decent in-ceiling speakers won't match the fidelity of good Hi-Fi speakers at the same price. A lot of that is to do with the way the sound fires at the floor rather than straight ahead and also a lack of back compression because the rear of the speakers are open in to a ceiling void or at best a leaky fire hood. However, the driver cones, magnets and crossovers can be just as high quality as their box speaker counterparts. A good pair of in-ceiling speakers are perfectly capable of showing the difference between a mediocre amp and a decent one.
HankMarvin, if you search Ebay for "amplifier kit" then you'll find the sort of gear that M3G4UK is probably referring to. These are cheaper versions of the HiFiberry because the component choices are made on price rather than sound quality. They all share a basic limitation on the real power they can deliver in to a loudspeaker.
If there's one thing that ceiling speakers need it's plenty of clean undistorted power. They're pointing at the floor rather than straight at you as Hi-Fi box speakers would, so straight away they're working at an acoustic disadvantage. You'll notice that the Ebay kit amps don't give a power rating measured in the same way as Hi-Fi amps (RMS @ 8 Ohm, < 0.05% THD, 20 Hz to 20 kHz). That's because if they were honestly rated then you'd be lucky to get 1/10th of the claimed power figures.
Here's an example of that. Velleman is a pretty decent amp kit manufacturer. AFAIK they do some fairly high-end gear too. Their smaller kits are competitively priced against the usual stuff tipping out of China. The Vellema K8060 is a dual mono power amp board kit priced at £15 exc heatsinks, power supplies and pre-amp front end. The claimed power is 70W @ 8 Ohm. That looks respectable enough.
However, if you look at the spec more closely you'll see that there's no distortion figure given and no mention of the test frequency. When they do give a power rating at "Distortion 0.02% @ 1KHz" then the power claim drops to 10W. Once again though this figure misses the crucial impedance. Is this 10W in to 8 Ohms or 4? If it is measured at 4 Ohms then when running in to 8 Ohm the power would halve. Also, 1 kHz test tone doesn't replicate a music signal, and there's no indication if the 10 W figure is instantaneous power (an easy thing to achieve) or sustained (RMS) which is much more difficult.
In the end even with a decent brand kit board the truth will out. These small inexpensive switch-mode-power-supply based amps can't generate clean undistorted power for sustained periods in to a real life reactive load such as a speaker. If you get 5W out of the Velleman on the same terms as the Yam AS501 then you'll be doing well. Meanwhile the Yamaha delivers a minimum of 2 x 85W RMS in to 8 Ohms @ 0.02% THD when driven with a 20 Hz to 20 kHz test tone that replicates real music. Game, set and match to the Yam and other proper Hi-Fi amps.
I want a good stereo effect, but I guess I could have this with just two speakers, just position them near the seating area.
but sounded fine after adjustment.