Typically car head units run out around 55w per channel.
Though this can be misleading as it depends on how the makers test and specify, one maker's 55 may be max before peaking, another's may be absolute flat out and a third may be RMS...all can be significantly different.
Similar with speakers although they often give RMS which does give a better comparison on what they can chuck out without distortion.

I would assume that the medianav output will be similar order.

In which case I would be wary that those may not work very well.
Even without the minimum power, general rule of thumb is that low power amps should not be used to drive high power rating speakers.
Issue is that although on paper a higher rated speaker will take all that the amp will put out, to get the sound output, you may need to crank up the amp to high volume and that can be where it starts to distort... cr4p sound or worse spikes that can blow the speakers.
Quick look I see that Halfords have very few 5.25 (used to have a good range) but for instance they have an Alpine set
https://www.halfords.com/technology...technology/car-audio/car-speakers/alpine-5-25-coaxial-2-way-custom-fit-speakers
35w RMS seems to be a better match for the assumed output of the Medianav.

What they sound like no idea and is very subjective anyway..... generally any decent coax will improve on generic in car speakers though but it's your ear and perception that counts, not mine.

In my Scenic BTW, I found that tweaking the settings made a world of difference.... for me, more to the rear, touch less treble and touch more base...sorta minus 1 and plus 1 really rounded out even the incar system. Was very flat and harsh with factory settings and front speakers working hard.

 

If you get after market speakers, you are really going to need to buy a small amp, or you will be disappointed, and end up buying one anyway

I dont know if it would work on yours, but on the Meg mk3, people are using the amp below, and i think it is small enough to tuck behind the dash

https://www.amazon.co.uk/dp/B00PAQGYKE/?tag=rsmeg-21

 

Im not expected to be blown away, just want a minor upgrade for now, my current speakers are only 5.25 so wanted some budget 6.5s in the hope it will improve the sound a little for now. I do plan on an active sub in the near future, or might go all out with a 4 channel amp and a passive sub, undecided on that atm though. Thanks for your replies!

 

did you end up going with them? if so how did they turn out?

 

How loudly any given speaker plays given the power input is rated in dB and is called sensitivity, the more sensitive the better the speaker at turning amplification into sound. These are 94dB sensitivity rated which is quite good, and would be far better than the factory fitted options. But to get them really moving, and producing good-mid bass you then start needing the extra amplification. The fact that the Clio MK4 front speakers come with their own enclosures and a downward firing port should help produce decent mid-bass without being pushed too hard - these will be louder at any given volume setting because they are more efficient, but the amplifier will be the limiting factor and they will sound distorted way before they would if amplified with an 80W RMS amp as you won't be using them to their full potential.

89dB sensitivity is middle of the road for after market speakers and we will never know the sensitivity of the factory units.

So anything from 90 to 98 is a good speaker at turning amplification into sound.

As an example - a 92dB speaker fed 20W RMS will be as loud as an 89dB speaker fed 40W RMS

To achieve a 3dB gain in sound pressure, needs twice the power input, so choosing the correct speaker based on wattage alone is not always best.

But, 20W to 40W is not twice as loud! - most accept that an audible increase in volume perceived as twice as loud as before is a gain of +10dB and to get that you would need 10 X the power input. So to double the sound you would need to provide 200W instead of 20W

Hope that helps anyone looking to upgrade any car stereo?