Well, I have been a fan of separates from the very beginning, and thus years ago spent a ridiculous amount of money on pre-amps (started with a Proceed AVP, then upgraded to Proceed AVP2), but soon realized that it was a losing proposition. Every few years there was something new, rendering the old system somewhat obsolete. The upgrade path was more expensive than throwing away and buying new.
Thus when I upgraded again, I decided to get the 'cheapest high end' (if there is such a thing) pre-amp. Integra (high end Onkyo) makes great stuff, but the Onkyo pre-pro is essentially a rebadged Integra, minus some tweeks, and 1 year less warrantee. I ended up getting a Onkyo PR
-885 directly from Onkyo but 'refurbished'. I cannot remember but it was essentially half the price of new but it was basically new, without a scratch. 4-5 years latter I am still happy, but now I want Atmos, and 4K pass through, thus it is time to upgrade again and so I just ordered the Onkyo RZ-5100 this time new (as they did not have any refurbished). If you search, you can find the 'street' price pretty reasonable. I am surprized that this pre-amp does not get more love here on AVS.
I have nothing but good things to say about Onkyo's pre-pro's, and for the most part they are built differently than the rest of Onkyo's receivers. The new pre-pro weighs over 30lb's. That is heavier than most receivers and suggests to me quality parts are used. I think people get turned off when they hear the name Onkyo which is to bad, because they are pretty good.