I had exactly the same plan when I went into the shop: Play the 3000 and 5000 next to each other and hear whether the sound difference was worth £90 extra. But on the day, although I couldn’t hear and appreciable difference at normal listening volume, it was the little things that made me go 5000, like the extra buttons that allow you to select sounds and drums quicker. Also the mic input. Also, don’t think of it as spending £300 vs £390. Think of it as investing £390 and owning the 5000 for a couple of years then selling it for £240, vs investing £300 and owning the 3000 for a couple of years and selling it for say £180. You have owned the better keyboard for £30!