Hi booffa, good luck with your next step.
Its interesting that the 3 machines you have narrowed it down to couldnt really be more different.
One question is do you drink mostly black or milk-based drinks?
I own an Oscar and have previously owned a Silvia. I have never used a Lusso but have read a lot about them as I have seriously considered buying one.
Briefly I would rate them like this:
Oscar - Entry level HX machine. Cheaper than other HX machines because of plastic exterior. Internal components still of high quality. Best option if making lots of milk-based drinks is important i.e. more than 2 at a time. Much more steam power than a Silvia.
Silvia - Great for low volume use. Great resale value and well made. You need to temperature surf to get the best out of it and also need to re-prime boiler manually. Not suitable for making more than 2-4 milk based drinks at a time.
Lusso - Probably best option if you are an espresso drinker although also has good steam power for milk. Levers are generally considered to have a steeper learning curve but most owners suggest the Lusso is relatively easy to use.
All comes down to what matters most to you I guess.
Also, have you considered the new Breville 900 which is about to be relased?
The 2 grinders you have chosen are a great choice. You may struggle to come under budget with some combinations e.g. Mazzer Mini + Oscar would be over $2k.