Upgrades for my system - I have Martin Logan Aeon,

I have Martin Logan Aeon, Hafler DH-200 Amp, Hafler DH-101 Pre, some cheap interconnects, technics CD player (c. 1994)
I would like to know where I can get the most improvement out of my system. I can upgrade the Aeons to the next speaker up until January with full trade-in value. The Hafler Amp is a little lop-sided, and I have to put the balance over to the left, but it works fine even after over 20 years.
I sort of just went through the same process. The hafler pre has good response ,just no soundstage . I'd get a new preamp, I got a PCA-2(to replace a hafler 110) and I love it. You will have to upgrade the cdp at some point. While you at it get some used Harmonic Tech Ic's for $100 on audiogon well worth the money.
I think your speakers are considerably ahead of the rest of your system. (I had a DH-200 myself, quite a few years ago.)

You won't really hear how good your speakers are until you've upgraded at least the CD, almost certainly the preamp, and probably the amp and interconnects.