Tube audio under $900?

So would the jolida 502 with KT 88s be an improvement?

The 502s are a big improvement over the 302s IMHO. Better transformers-better bass and dynamics regardless of el34s or KT88s. But you can get point to point wiring in the Cayin or Prima Lunas and skip the circut boards for the money you are talking about.

I agree with Sufentanil. Anything in your $900 price range will basically be a sideways move from the 302B.

Depending on your goals for the change in amplification, you might contact Undwerwood HiFi and find out what mods they would install for your $900. It'd result in improved clarity and frequency extension...perhaps also some improved bass clarity.

Otherwise, I'd save your money until you can afford a significant upgrade.

Bottlehead and Decware. So overlooked small manufacturers with no advertising budget and stellar product.

Used cayin will give you great sound and value.b