Upgrade Suggestions

I'm getting the upgrade bug and would like some suggestions as to what you think would have the biggest impact based on my current system. My first change was from a rega planet to the Linn Ikemi and it made a big difference. I'm not interested in sacd at this time and would like to stay in the 3-5k range, with trade in of whatever is replaced. I listen mainly to jazz, acoustic guitar and vocals. Thanks.
If you haven't already upgraded your AC to dedicated lines, that would be an excellent place to make an upgrade. You can also experiment w/PC's & outlets. Tune your room too & spend the rest of your budget on music.
Driver is pretty much right on the mark. Answer to your biggest impact question: I would argue that changing speakers has the largest impact on a stereo system all else being equal.