For $4k, you'll be able to get a fantastic grinder & machine. It will simply come down to personal preference for different features. You really should do at least two things, 1) familiarize yourself with the types of machines
here and
here and
here. 2)Start reading
reviews on this site.
Depending on your needs/desires and the fact that you only make espresso, it may be as simple as a
Quick Mill Alexia with PID control which is arguably regarded as one of the best espresso only machines. And a great grinder like a
Mazzer Super Jolly. But no matter what you do grinder first, grinder first, grinder first! Don't skimp there.
Edit: But if you're ever going to steam, even for guests then look to an HX or DB over a single boiler like Alexia.
Living the caffeinated life.