Hehe. Never say that - you'll just encourage some totally contrary opinion like this one:
If you have budget limits - dump all your optical. Rip it and sell all the discs and players before they drop further in price. Sell the Pono. Get a laptop with Realtek HD Audio (pretty standard), or get an external $100 garden variety external Async USB DAC 24 bit for an existing computer. You can very well find the laptop used, you can just wipe it and use it exclusively as a player.
Given that I just picked up 3 decent microSD 128G cards around $70 each, optical is a dinosaur. The cards are the size of a fingernail. There is no scientific difference to optical, and the sound I reference above is transparent. For on the go use any high-end smartphone or pick up a 16 bit player the size of a quarter for <$100. Use any solid state combined pre-amp amp that is transparent if you have speakers. Avoid a headphone amp if you can. I believe you can get the total electronics in the $1000 neighborhood. Spend every cent you collected from the sales and savings on transducers - you can get lots of help on this forum on your budget and how to divide it between cans and speakers. If you don't believe it is transparent, ABX it before you sell it.
Game, set, match, jump over the net and hit the ball into the stands.
I don't have anything against Pono - I think the store is interesting. But you are in sound science and that's my opinion.
But like I said - you opened the floodgates