I've found a second-hand Ryzen 7 7800X3D and RTX 5070 together for under NZ$1,700. I already have a 1TB drive and a 650W 80+ Gold power supply. What affordable, compatible parts should I choose for the rest of the build? I'm mainly wondering about the motherboard, RAM, cooler, case, and whether the 650W PSU is sufficient. Would this CPU and GPU combination be well balanced, or should I expect any major bottlenecks? Since the CPU and graphics card are used, I'd also appreciate advice on what to check before buying them.
3 Answers
The pairing itself is strong and should be well balanced, especially for 1440p gaming. For the rest of the build, look at a B650 or B650M motherboard, 32GB of DDR5-6000 memory, and a decent air cooler such as a Thermalright Peerless Assassin. You don’t need an expensive liquid cooler for the 7800X3D. A micro-ATX board and case can help keep the price down, as long as the case has enough room for the graphics card and good airflow.
I’d seriously consider replacing the 650W power supply. It may run the system, but the RTX 5070 can put the PSU close to its recommended limit once the CPU and the rest of the components are included. A quality 750W unit should be the minimum target, while an 850W ATX 3.x or PCIe 5-compatible Gold model gives you more headroom. Also check the PSU’s age and condition before reusing it.
A sensible budget setup would be a B650M Wi-Fi motherboard, 2x16GB DDR5-6000 with a CAS latency around CL30–CL36, a Peerless Assassin-style air cooler, and an airflow-focused micro-ATX case. Use two matched RAM sticks rather than starting with one 16GB stick; dual-channel memory performs better, and buying a matching second stick later is not always guaranteed to work perfectly. Make sure the motherboard BIOS supports the 7800X3D and verify the used CPU and GPU for damage, tampering, overheating, and stable operation before committing.
That’s really helpful, especially the advice about buying a matched 32GB kit and checking the used parts. I’ll compare the cost of a new 750W or 850W PSU before finishing the build.