You say you’ve decided to buy a solid state amp.
Here are some questions to consider:
1. How loud do you normally listen?
2. What’s the maximum loudness you ever expect to play your system at? For how long? (Like, are you hosting a party and need the music to play loud...
IMHO, the question you’re asking grossly oversimplifies things. Which can lead to misleading conclusions. I’d be curious to know what kind of music you like to listen to, what sources you prefer, and what you have enjoyed about your system or other systems you’ve heard.
I suggest you download a simple sound pressure level meter for your smartphone (assuming you have one). I use decibel X Pro. It’s good enough for my purposes, and I suspect, yours.
Use this to find out how loud you normally listen. You might be surprised to find you’re often using less than one watt. IMHO, 89 dB is loud! When I go to live shows the volume is often right around 95dB, and that is loud enough that I often use hearing protection.
If you’re listening to music below, say, 80 dB, it opens up many intriguing possibilities towards the low-powered end of the spectrum. A lower powered amp, thoughtfully evaluated, might be able to use a simpler circuit. Sometimes a simpler circuit can sound better. I prefer a very low parts count and feel fortunate that I can get by with about 1.5 watts. Higher powered amplifiers can sound different, but not necessarily better, unless I’m listening really loud.
Oh, one other suggestion - track down Markus Sauer's thinkpiece, which was published in Stereophile, titled "God is in the Nuances". Worth reading.