iMac 18,3 with dual external 5K monitor

I would like to run a iMac 18,3 (Radeon Pro 580, i7 4.2 GHz) with two external 5K monitors (LG 27" 27MD5KL). In Apple's description (https://support.apple.com/kb/SP760?locale=en_US) I found: > Two Thunderbolt 3 (USB-C) ports with support for: > > DisplayPort > Thunderbolt (up to 40 Gbps) > USB 3.1 Gen 2 (up to 10 Gbps) > Thunderbolt 2, HDMI, DVI, and VGA supported using adapters (sold separately) However, this document also states that two 5K external displays are not supported: > Simultaneously supports full native resolution on the built-in display > at 1 billion colors and: > > One 5120‑by‑2880 (5K) external display at 60Hz with support for 1 billion colors, or > Two 3840-by-2160 (4K UHD) external displays at 60Hz with support for 1 billion colors, or > Two 4096‑by‑2304 (4K) external displays at 60Hz with support for millions of colors Is there anything I could do to run two external 5K monitors? E.g. replace the iMac's graphic card or use an eGPU?