I might have been the one who bought those 300’s😄. So far I am really enjoying them.
Congrats! Those were very tempting for the price.
Which tubes are you currently running? I found the 6DJ8 Amperex A frames (~$70/pr on eBay for NOS) to be a great reference tube. They do everything well, excellent imaging and very balanced across all frequencies. Great place to start if you're running stock tubes, especially since they're easy to find as NOS and reasonably priced.
My current preferred pair is a set of Westinghouse 6DJ8 medical grade tubes (likely rebranded Mullards) that have more of a 'live' feel to them, which win out slightly over the Amperex. I tried a lot of others ranging from Valvo to Russian NOS to BHK recommended Tungsram, but the Mullard and Amperex tubes sound best to me so far.
For reference, the BHK 250 even manages to drive my MBL 101s at moderate listening levels. Great amp with plenty of power for most speakers.