Upgrading from 2x 3090 - what should I add? (2x A6000/5090/48GB 4090?)

I'm in a position to upgrade from the classic dual 3090 setup to something that can run the next step up, eg 100-110GB+ model files. I've got an asus x299 ws pro and a 1600w PSU, with 128GB ram, and I want to add to my 3090s, rather than replace them. I'm trying to weigh up modded 4090s (2x48GB), 2x

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I'm in a position to upgrade from the classic dual 3090 setup to something that can run the next step up, eg 100-110GB+ model files. I've got an asus x299 ws pro and a 1600w PSU, with 128GB ram, and I want to add to my 3090s, rather than replace them. I'm trying to weigh up modded 4090s (2x48GB), 2x