OP: ”I ask because I‘ve got a $5k TT with a $2k cartridge on it and am trying to figure out whether it’s worth investing in a really good phono preamp or not.”
This is a really important question to ask, particularly at this time. Digital is finally making strides to make parity with digital. The cost of acquiring disks, even if used is significant… while streaming is much lower ongoing cost with the benefit of a nearly infinite library. If you are future oriented, I think the answer is simple and clear… digital.
I have 2,000 pristine, many audiophile vinyl discs… and have experienced analog… well since born nearly 70 years ago. So I maintain and enjoy my analog end, but only 5% of the time or so since I have an equivalent digital end. If I was younger, no question I would put all my money into digital to get the best I could afford. It is now the future (as opposed to the CD promise 35 odd years ago). Splitting your money with two approaches is not going to be as effective as one.

