I think that if the Yamaha ticks all your 'must have' features box then go for it. I'd definitely buy other speakers though.
In the £250~£400 price range, the go-to products for sound quality are the Denon DM-41DAB (£249), the Yamaha, and the Marantz Melody/Denon CEOL. These latter two are two brands from the same parent company, but tailored for slightly different markets. In addition, Melody and CEOL are product ranges rather than specific models, and so you'll find different versions at progressively higher prices.
There's also the Cambridge Audio One at around £350. However, like the Denon DM-41, it doesn't really compete in feature range with the Yamaha.
Traditionally, Marantz has been the brand for those more interested in music playback whereas Denon has targeted those looking for power or value. This is certainly still the case with surround sound amplifiers and AV receivers. The boundaries are a little more blurred though with the mini Hi-Fi systems as it's harder to make like-for-like comparisons.
One point to note is that Marantz seem to have had a bit of a rough ride with product reliability on the Melody range over the last couple of years. I would read customer reviews quite carefully on that one before pressing the buy button.
Speakers:
IIRC, Denon has offered some of its mini systems with speakers in the past. I think they went to Mission and maybe Wharfedale too at various points.
Yamaha is one of the few electronics brands that also makes musical instruments and does speakers. However, the company has never been known as a volume brand for bookshelf stereo home audio speakers in the UK. It's just too tough a market for them to crack. The UK is home to many of the world's finest loudspeaker manufacturers, and small bookshelf speakers is our bread and butter.
It's not possible to tell everything about a pair of speakers from the specifications alone, but a couple of standout points to me with the Yamahas are the relatively low sensitivity (83dB/W/m) and the 6-Ohm impedance rating. Neither are huge problems in their own right, otherwise the speakers wouldn't be sold with the n470. However, they do highlight areas where a third-party product could make a useful improvement.
If you haven't come across sensitivity before, it gives an indication about how well a speaker will do at converting amplifier power in to sound. The higher the number the better. For small bookshelf speakers in the £100-£200, 85-87dB is typical. To put this in to perspective, the Q Acoustics 3010i (£159) are also 6-Ohm speakers but have a sensitivity of 86dB. They need just half the amplifier power to sound as loud as the Yamaha speakers. The n470 doesn't have a lot of power to throw around, so anything that makes better use of that power will help to keep more power in reserve ready for when the music needs that shot of dynamic punch.
The Ohms rating is an interesting facet because it works counter-intuitively. You might expect a lower impedance speaker to be a better choice since it offers less resistance. It's a little simplistic, but if you think about impedance more in terms of the length of a spring: bigger = longer, smaller = shorter, then like the springs of a car suspension, short springs take very little compression before hitting the end stops. Longer springs offer a smoother ride. In this analogy, a smoother ride equates to the amplifier being asked so supply less current.
What's happening in the amplifier is that a higher Ohms load is an easier load. Amplifiers don't push power in to speakers. Instead. it's speakers drawing power from the amp. What the amp does is to create a voltage across the speaker terminals. The speaker voice coil reacts to that by creating a magnetic field to move the speaker diaphragm. In other words, it does some work. Since work requires energy, and the source of that energy is the amplifier, then that results in a flow of current. If we know the impedance of the speaker (say 8 Ohms for the R value), and the voltage across the speaker terminals (lets say 8 Volts in this example, though in reality it would vary with the music content and volume setting) then the current drawn (I) is given by the V/R. This gives us 8/8 = 1, so the current drawn is 1 amp.
Changing the speaker to a lower impedance - say 6 Ohms - results in more current being drawn rather than less.
V/R = 8/6 = 1.33... The amplifier is being asked to deliver 33% more current to push the speaker diaphragm the same amount of distance and do the same amount of work.
The fashion of measuring amplifier power at 6 Ohms rather than 8 Ohms is to artificially inflate the result. If we want a power figure in Watts, then one way of calculating that is to take the square of the voltage (V^2) and divide by the Ohms (R). Our 8 volts from the previous example becomes 64, and then divide that by 8 Ohms gives us 8 Watts. Repeat for a 6 Ohms load, the result is 10.66 W which is an apparent 33% increase in wattage. What they forget to mention is that the amplifier is working 33% harder delivering 33% more current. There's no such thing as a free lunch.
In speaker design the nominal impedance can be anything the designer wishes; and there are some valid reasons for choosing a lower Ohms value in certain cases with higher-end speakers where there's enough money thrown at a system that amplifier power really stops being a brick wall concern. However, with lower cost systems this isn't the case so much, and so going for a lower impedance is more about cost saving in some way.
Some recommended speakers:
Wharfedale Diamond 220 - 8 Ohms, 87dB, 55Hz-20kHz, £119/pr
Fyne Audio F300 - 8 Ohms, 87dB, 55Hz-28kHz, £199/pr
Dali Spektor 2 - 6 Ohms, 85dB, 55Hz-26kHz, £179/pr
Mission LX1 - 6 Ohms, 87dB, 65Hz-26kHz, £119/pr
Monitor Audio Monitor 50 8 Ohms, 87dB, 55Hz-30kHz, £160/pr
This list isn't exhaustive, but it gives you an idea that above and below the Yamaha speaker price there are some other options to consider.
