Under $1k. $999. I would pick RME adi2. I owned this DAC for a few years and it's hard to beat for the money.
Under $5k. $3300 After looking at several DACs between $1500 and $6000 I chose the Lab 12 DAC 1 Reference. I love this DAC. Not feature rich , in fact it's pretty stripped down but sounds great. Can listen for hours without fatigue.
The best DAC i have heard in person is the MSB Discrete. I would buy one if I had the means and a system that could exploit it.