Ah, I confirm your input that SLI does not double the video memory. But I believe people have taken the whole DisplayPort is the only way to far. HDMI 2.0 does in fact give 60Hz for 4K, I have it set to mine in Nvidia Control Panel.
But back to the OP's question, I have no issue with a 4k TV over a Monitor. I understand I will never see 120 FPS on my TV at only 60Hz but I don't believe you could possibly tell a difference between 60 FPS and 120 FPS in DCS unless we start doing FPS in CA.