stereo amp vs monoblocks, any advantages?

Good question.

I'm stretching here a bit , but the main advantage I can see for monoblocks versus say a dual-mono single box design is that you get a dedicated power cord to each side. That would be beneficial I think if the amp draws a lot of current andassuming your power circuits are capable of delivering more current to each this way than otherwise.

There may be some advantages in exposing line level circuitry in the amp to lesser EM fields produced by a single power transformer nearby rather than two as well.

That's all I can think of.

Better isolation between left and right (lower noise potential and less distortion) is probably the most distinct advantage, but even so, either should sound very good and a very discriminating ear might be needed to really hear a difference, all other factors aside.

Two cords might be able to draw power more efficiently than one even on a single circuit, not certain about that though.

I think two circuits can be done in a manner that avoids possible issues like ground loop hum, etc. if needed. A single circuit for very high power amps might be a limiting factor though I believe.

Shorter cables are generally better.

So is better isolation between components and between components and external EM fields from nearby transformers, etc.

Minimizing these somehow are the factors to consider in a setup for best possible sound.

Also low level signals, like low level phono setups, are more susceptible than higher line level setups. Speaker connections are susceptible as well but to a lesser degree based on my experiences.

"Are there advantages to monoblocks? Maybe. "

The advantages are real in theory in regards to optimal sound and worth being informed about.

In practice they may or may not matter much from case to case.

And, other factors generally come into play that are more important, like convenience.

Few setups are optimized to the nth degree (well some on this site are perhaps) and still sound great. My system certainly falls into that category.

If I were a vendor selling products or services to others rather than your typical Joe music lover, I would probably pay the nth degree of attention to these things. Otherwise, it really may not matter practically.