You don't need a second 8.33 radio to be IFR compliant if you're operating under Part NCO. The second radio can remain 25kHz ans used only on specified retained frequencies such as 121.5.
Even though Part.NCO only requires one COM for IFR, to my knowledge the fight is still open with some NAAs trying to sneak through the back door, even if this is in contrast to EU regulations. We'll see who wins.