The best deal, right now, in a good room, is the Epson factory refurbished 5040. It has a 10Gb/s HDMI port, which limits 4K content to 24 frames per second. This generally isn't a big deal, but isn't as future centric as the newest models from them.
But, the black levels are going to be, by far, best in the price range.
The wireless Home Cinema 5040UBe projector takes color and detail to new levels. Featuring 4K Enhancement Technology1, the 5040UBe is the World's First WirelessHD Projector with 4K Content Support. It's also compatible with High Dynamic Range (HDR) content, displaying an extraordinary range of...
epson.com
It includes a 2-year warranty. I might opt to spend a bit to extend that warranty if you can.
Otherwise, you are in the pixel-shifter 4K price category, not the native-4K price category. At the consumer level, only LCoS delivers native 4K resolution, and only Sony and JVC are doing this. Sony you can get for a bit less than JVC.
Contrast is another discussion. Once again, it is Sony and notably JVC which delivers best in class contrast. It is almost ubiquitous that those who really are into home theater, know their stuff, and have some money, put a JVC into their space. The pixel shifting JVC RS540 is out there for about $3,500 or so, and their better models with native 4K are another $1,000 on top of that.
The DLP models at the entry level are decent performers. But, they are contrast limited with more of a 'grey' black vs. a OLED black. So, like a cheap LCD TV, or even worse. The Epson 3200 is a decent entry level pixel shifter, but it won't perform much better than the DLP models.
The Epson 5040 was just recently upgraded to the Epson 5050. It was a very solid performer with best in price performance when it was closer to $2,500 new. But, at half that price now for factory refurbished models, it is, by far, the best deal going for price/performance value.
TO YOUR OTHER QUESTION:
I would also like to know What kind of brightness differences I should expect in brightness and black levels (in a blacked out room)?
This isn't a question which makes a lot of sense.
On screen brightness will depend on the projector in use and the size of the screen. Contrast will depend partly on the projector, but a BLACKED OUT ROOM means that you have painted the walls and ceiling a near-black color and you are using near-black carpet. If you have a large white (reflective) ceiling, and light walls, and beige carpet, you are a long way from a blacked out room. It's just a living room with the lights out after dark.
So, contrast will greatly be impacted by the room you put the projector into. Brightness will be greatly impacted by image size.
Screens can help/hurt things depending on your setup.
You didn't say much about the room or the projector location. You can't just drop a projector wherever you want and call it done, so that's a consideration as well. You also will need to consider audio in the room.
Calling things 'typical', with a 15' or so deep room, and a 12' seating distance from a 135" screen, the Epson 5040 will perform with excellence.