u/CoSonfused

I have my own countertop, it's 180cm*80cm*3cm of solid wood. It's a HEAVY sucker. I also want to add additional 1.8 cm thick MDF plank(s). The idea is to add an outfacing LED-border around it, and this will make it easier and cleaner, I believe.

I'm thinking of placing my pc above the Alex cabinet, so I figured I'll add an extra leg behind it, since it's so deep. But as the title says, I'm worried about sagging.
Will I need an extra leg in the middle? Even with the heavy solid top and extra planks?

I don't plan to add much weight in the middle, just two screens.