Just replaced some of my 345w panels with 580w panels.
They work together in series just fine, but I lose a little because the older panels limit the current of the newer panels. Recon I'm getting 400w out of the 580w panels, but I'm also getting the advantages of the newer tech, and the much lower prices. These Rapid 580w are between 2,300bht and 2,100bht (with vouchers) inc delivery.
https://www.lazada.co.th/products/i5031706101-s21274917764.html