plus an audio port.Looks like 2 x HDMI, 2 x Display Port, 1 x Thunderbolt, 1 x USB 3.0? 4 x USB.
Inspiron 620 - that's got to be 6 years old by now. Make sure you get a card that doesn't require extra power - and even then, that old power supply might be a sticking point. I'd make sure I warned him about potential problems due to the age of his system.
What is it going to be used for - probably hard pressed to find dual HDMI as most are going to Display Port now.
MSI GTX1050Ti has x2 HDMI,Display Port and is low profile.
Man those new monitors are too nice for that Inspiron! U2415? I would be pushing for a nice Optiplex 5060/7060 running those off the two DP on the motherboard.