Those models look absolutely stunning! I think that the Old look you guys are going for is great for showing the gap between Black Mesa and Half-Life 2. Keep it up!
I noticed in this and your other posts that your redone / new models are very detailed. Of course, this makes them look more pretty and realistic, but I would guess that it also results in a higher polygon count (more faces / vertices per model).
Is there any significant increase in polygons in your models in comparison to the models from the first release? And do you create additional low-poly models that get displayed in place of the high-poly model if the player is far enough away to not notice? (If I remember correctly, that is the / a way you could use both very detailed models and huge open areas in source.) Or do I underestimate the power of modern graphics hardware?
Another, (although related) question: Do you first create a (very) high-poly model and use it to bake normal maps or do you start of immediately with the model that will end up in-game? (and add your normal maps by other means later on?) i.e., these nice untextured work-in-progress models like the one in your latest blog post look like they will end up in the game as they are (textured, of course).
And, of course, I have to say that your models are really well done and have a nice industrial and vintage feel to them. You seem to go for the more serious / less cartoony style, which in my opinion fits the story and game well.
Finally, I am always looking forward to your development updates, please continue making them 
What you are calling high poly is a misnomer they aren’t huge by modern engine standards, somethere around 5-7k for the consoles. They are larger by maybe 25-50% than the one they replace, mostly in the details. They can always have several levels of LOD if needed. I’m newer to modeling and I don’t go the HP route first. I do mine in reverse because I’m starting with a base model redo. It’s easier for me to do most details with ndo2, but I’m learning new stuff all the time.
Thank you for the answers
Have you ever considered doing your models the other way around, i.e. high-poly first? Maybe not when you have a base model to start with, but if you do something from scratch? And what are the advantages / drawbacks of creating models without a high-poly basis?
Well doing HP first is the usual way it’s done. You the retopo the model to make the LP or remove edge loops. The advantage is you have all your detail done, you just bake all your maps then texture. I didn’t learn that way and most the props I’m doing are improvements or remakes so there is already a base to work from.
That’s quite impressive.
Finally the stuff doesn’t stick out like a sore thumb.
I am not sure I am not gonna miss the old models though. They are wacky and look like they have escaped from a recording studio, but at the same time they look cool as fuck.
Well the new ones combined several vintage recording consoles.