How many watts??

Sorry, but the speaker manufacturers and hi-fi world in general have fed you so full of irrelevant BS it is easier to just ask, what is that you have now, and what are you trying to do?

It is impossible for us to know what 1/4 volume means in terms of volume. Then there is the efficiency of your speakers.

There is no such thing as too much power. If you are happy with what you have do not change it. 

I have Marantz receiver which is 16 watts per channel.
In order for it not to clip I roll off bass with tone control, because 16 watts isn't enough technically for any modern speaker on the market.
Currently it's driving B&W C202 tiny bookshelf speakers

"...what is that you have now, and what are you trying to do?..."

This. We can help you a lot better if we have some details. We have been doing this a long time. Whatever you are trying to do, we've already done it. 

VU Meters were all the rage in the 60’s and 70’s… McIntosh being one prominent adherent well into today. Big reason why they were dropped was because a lot of people noticed they were not using that much power to “swing the needles” 

So trying to sell a triple digit amp when people were armed with knowledge didn’t seem like the path capitalists wanted to take. Some manufacturers even build power hungry speakers just to sell their big watt amps… see above for example.

The total power of a amplifier should be taken with the knowledge that you should have enough headroom for dynamic passages. Lots of amps will run in pure class a for the first few watts. You also should take into account the load the speakers present. Inefficiencies will require power.  For example, you could run a pair of very efficient horn speakers, like Klipsch with a modest few watt tube amp and enjoy satisfying volume.