A tade more briteness - Jolida 302b. Tubes?

If you are running stock tubes, then absolutely, you can get more open highs with a tube change. Cabling can also bring out more in the high end as well. I'd start with the tubes at the source, and even a power cable on the source. When I had the Jolida JD-100 (is that the model you have?), it really came to life (much better frequency extension, less constriction on the music) with a good pair of NOS tubes and an upgraded power cord. Lots of info in the archives on various options for that player. The other source of constriction is often the interconnect cables. If you are using Signal, consider trying something like Analysis Plus Solo Crystal, Luminous Audio Synchestra, Z-Squared Au/Au, etc. When it comes to cabling, my recommendation is to keep an open mind, pick a price limit with which you are comfortable, and if you buy used, you can always re-sell (at no loss) those that don't work for you.
Very nice system. Enjoy!

Cables and tubes are "tweaks" as far as I'm concerned, and shouldn't be relied on as tone controls.

Man, is this a tiresome refrain, and one that has no application in this instance. You are not looking to change the tone. You are looking for high frequency access. The information is there, on the source disc, and experimenting with cables/tubes in your situation will absolutely yield the result you want. End of story.