That all makes sense.
First, I have never heard the HiFi Rose - what’s it like?
Second, can you use the single-channel 72 as a pre-amp just for the one channel of the Uniti, just to serve until you can get a serviced and working 72 or 82? I am surprised it works at all if it is completely unfixable.
I don’t know about US pricing, but I did look at eBay. That suggests a bit over $1000 for a 250, with a Hicap costing a bit over half that (and as with power amps servicing any Hicap over about a decade old may need to be considered if it has never been done). Preamps look a bit rarer, with 72s costing over $600 and 82s a bit over twice that. Note that a 250 won’t power a pre-amp, hence the Hicap is needed if you get a preamp that needs powering.
Have I got those costs about right?
In any event, we can see what others here think, but if I were in your situation, I would get a decent 250 as soon as the opportunity. I would also want an ‘in principle’ or ‘if I can find one’ preamp decision, because if I will be getting 72 or 82, then I know I will need a Hicap. Of course, if you are not at all likely to get a preamp, then you won’t ever need a Hicap.
Bear in mind that there is nothing bad about stopping where you are or at any stage. This is important, because, if you have (say) 82/Hicap/250, then arguably they will be showing up that the Uniti is a good source but not a perfect one. This is a slippery slope that leads to a different streaming source, or a different DAC or a different CD transport or more than one of the above. Pretty soon, you have 5 or 6 boxes (plus speakers or headphones) just to listen to music.
If you get that far down the road of upgrades, you may feel the need for a dedicated rack, perhaps even a Fraim. However, for pure sound-per-$, I’d be surprised if that was top of your priority list any time soon unless the boxes will be sitting on something really weird/ unstable.
Good luck!