Board search result = Area-51 R2, graphics card upgrade?

In all honesty that is an older system and pending on what graphics card is currently used in it, there's not going to be much of an upgrade path in terms of performance.

Again, it all depends on your current graphics cards.

If you really like your Area-51 R2 and you don't care about Vanadiel logic and economic practicality you can max out your CPU to i7-7700K for about $350.

Logical my dear Watson, logical.

What does his CPU have to do with his graphics card question?

If they want to get maximum benefit out of an upgraded graphics card, then they should max out the CPU. There is no limit to the graphics card that can be installed in the Area-51 R2 . . . the CPU will become the limiting factor.

The graphics card is:

NVDIA(R) GeForce(R) GTX 1080 with 8GB GDDR5X

Given the info presented here, at what level of graphics cards does the card start to outpace the current CPU?  

GTX 1080 is the graphics card you have now . . . or the graphics card to which you are upgrading? Because that is far below "the max card that this unit will support".

If you are only 'upgrading' to GTX 1080 (a nice graphics card, by the way) then your current CPU is fine.

 The 1080 is the current card.  I'm exploring upgrades from there.

If you are not upgrading your CPU, then I don't see much benefit in going above perhaps the RTX 3060.