You need a powerful preamplifier to drive the high load of 4.4 kΩ, with an output impedance as low as possible to drive it with enough current and capable of 9V. For this I would choose a preamp with dedicated substantial transformers.
Topping Pre90 and D90 preamps might be a toy for this load. They have low output impedance and high voltage output level at high gain, but how can it pull oscillating current at low voltages, that's to say normal volumes?
I never liked Topping Pre90 or D90 because they both hide in specs that they have a high input impedance of 2 kΩ in XLR. What do you do if you have a ladder dac like a Denafrips Ares of 1.2 kΩ output impedance? It can't drive the Pre90, so the problems start there.
Everybody seems to use these Topping preamps with the Purifi. If you want to bypass the input buffer opamps, which are no substitute for a proper preamplifier by the way, choose a powerful one. Not just low output impedance or high brute voltage, but 'cojones' from the transformer to pull from the load at low voltages. The input buffer from the Audiophonics using opamps and big value resistors is the easy way to bring up the impedance, but this is rather a compromise (noise from the resistors and the opamps changing the sound).
This is my two cents.