A 400GB card is about the largest you can find these days. You don't have to worry about speed, though - for music, even a U1 is more than fast enough. (For 4k video you need a U3 card.) SanDisk is the best one out there, but it's a bit more expensive than most. (But their tech support is not only great, it's online if you want it quickly. And, having spoken to a few of their tech support people, I think it's worth it - they're really tech support people, not "associates" reading scripts in heavy accents.)
If you don't think you'll ever have that much music, you can go down to 256GB, 128GB or even less. If the tab supports 64GB (and that one does), it supports up to 2TB (even though the specs say 256GB - it's up to the technology - to support 64GB or more it has to support SDXC, and that goes up to 2TB). Don't buy too small, and be left with having to buy a larger card, but if you have a 20GB music collection, even a 64GB card would be more than you need (and pretty cheap compared to 400GB).