It depends on your own use ... in the future, you plan to take a professional route ... that is, to run around for a living ... and then you can consider upgrading ... If it's just a hobby of playing with a group of friends ... personally, I don't think it's necessary to upgrade ... After all, you said that the piano and box are more than 3,000-5,000. ..

As for which is important ... I think both are important ... It is not good to have a good sound source (guitar) ... It is also necessary to have a good communication medium (speaker) ... If you can only upgrade at a high price in the short term, I suggest you upgrade the speaker ... The reason is that the sound produced by a good speaker is faster than a good guitar ... and the price is relatively cheap ... because the piano has reached the stage of 5000 ... unless you buy it. ..

I hope it helps you.