Keep the 155
This is same situation as myself. You legally need one 8.33, so change the 196 to radio of your choice, and continue to use the KX155 as nav only after 1 January. You'll also need to placard the com side to say 121.5 only - as you can still use in emergency after that date. There may be some other 25 spaced frequencies that will be preserved, but realistically your new radio will be Com 1 and you'll never need the 155 voice unless your new kit fails.
I've changed my MX11 for Garmin 255a, and kept KX155 for loc/gs. Also swapped IC-A20 for a Yaesu 750L, so that I have handheld back-up (and the Yaesu has GPS too).
All the above is true if your IMC flying is like mine (using IR/R rating outside the airways). If you go IFR and into controlled airspace, you'd need full airways kit which includes 2 x 8.33, 2 x altimeter etc etc. Which is one reason I never took the IR rating.........
Suggest you do sooner than later so you can claim rebate in first tranche before they run out of advance EU payment.