Here are my recommendations for RAM to pair with an AMD Radeon RX 7800 XT for a high-end gaming PC:

RAM Speed:

• For optimal performance with a high-end AMD GPU like the 7800 XT, I recommend going with fast DDR5 memory
• DDR5-6000 with tight timings would be an excellent choice to fully leverage the capabilities of the 7800 XT
• However, DDR5-6000 is quite expensive currently. DDR5-5200 or DDR5-5600 with good timings will still provide very strong gaming performance while being more affordable

RAM Capacity:

• For smooth gaming at 1440p and especially 4K with a powerful card like the 7800 XT, I recommend getting 32GB of RAM
• While 16GB is still sufficient for most games today, some newer demanding titles can utilize more than 16GB at very high settings and resolutions
• 32GB will provide some futureproofing and ensure you don't run into any RAM constraints, even in the most intensive scenarios
• It also allows you to multitask more freely, like having a game open while streaming or running other applications in the background

In summary, my suggestion would be:

• Get a 2x16GB (32GB) DDR5 kit
• Aim for DDR5-5600 or higher frequency if budget allows
• Prioritize kits with tight timings like CL36 or lower

This will provide an excellent RAM configuration to complement the 7800 XT for high-end 1440p and 4K gaming, with enough capacity for the most demanding titles and multitasking.

DDR4 RAM with AMD Ryzen 5000 series CPUs are also good choice.

 Unless you're doing serious productivity work, 16GB of DDR5 should still be plenty for gaming with a 7800 XT. I'd suggest these 16GB kits.

Take a look at top selling DDR5 RAM on Amazon.

I recommend G.Skill DDR5 RAM.