You are misunderstanding how power works.

Volume is LOGARITHMIC, it is not linear. What does this mean for power? It means that power is dynamic in relevance to the volume you're trying to achieve with the speaker. Simply because the receiver is outputting 90w over 2 channels, it DOES NOT mean it is feeding 90w from 20db to 75db (as an example).

Let's take the Wharfedale D12.2 as an example, its sensitivity is 88db @ 2.83v over a 1 meter distance. This means it takes ONE watt, yes ONE watt to reach 88db of volume if you're standing 1m away from the speaker with no reflections (this is why specification numbers SHOULD NEVER be taken as a real world indication because speakers are spec'd in an anechoic chamber).

Trust me, your ears will give up first long before you even reach 90w of usage from the receiver.

So why do people want 500w per channel for a single speaker then? What's the point of mono blocks? Because in the real world, you don't sit 1m from your speaker unless you're doing a desktop setup. Then there are considerations of other drivers within a speaker. Bookshelves are usually 2 ways (tweeter - woofer), so not much needs to be said about them. But towers which are 3 way (tweeter - mid woofer - sub woofer)? Those need power and that's why towers are usually more efficient than their bookshelves counterparts due to coupling of drivers and crossover networks.

You should also understand that the higher the frequency, the less power is needed. This is because the human ears are most sensitive between the 800hz to 10khz region. Reaching 75db around these frequencies requires much less power than reaching 75db at say low bass frequencies in the 20hz region.

Power is a very long and complicated topic. As a beginner, all you need to know is that you shouldn't get caught up with all the hype around power. It's easy to get loss in it because humans always relate to bigger numbers = better.
My opinion is always try and get a sub (well multi subs actually) to couple them with the bookshelves. Let the sub handle the bass and let the bookshelves handle the mids and upper frequencies.

I've never liked to use the audiophile terms of describing sound. To me, it sounds very stupid. "Warm" for example is such a vague term because bass is from 0hz to 300hz. Which part of it is warm lol? It's more straight forward to describe the issue in the round number octaves of frequency range, rather than blanket it with a single term.