Mine is about 3000 psi and it is adequate for everything I use it for, mostly things like you listed and washing the car occasionally. I don't think I would go much lower than that. I also used it to strip old paint off the barn before I painted it, and it worked great. The highest pressure nozzle will actually wear a hole through old, worn, weathered plywood.
Mine is a Craftsman, but I just ended up with it because Lowe's had it marked down to almost half off with a note saying it wouldn't build pressure and wasn't covered by warranty. I figured at worst, I might have to replace the pump. But fortunately I decided to test it before I started tearing the pump apart, and it was working perfectly. I suspect someone took it home, used it to clean what they wanted to clean, and returned it for a refund claiming it didn't work. But IF it's not building up pressure, I'd hate to see what it does when it works!
Aries
~Sign of the Rams