What’s the best cheap upgrade for my old Core 2 Quad PC?

Before buying anything, check the motherboard model, power supply, and local used prices. With a system this old, compatibility and what parts actually cost where you live matter more than a one-size-fits-all recommendation.

If you can find a compatible card such as a GTX 750 Ti or GTX 950 for very little, it could be a substantial step up from the GT 610. Check the card’s power connector and the PSU’s capacity first. The Q6600 and 4 GB of RAM will still limit newer games, though, so a GPU swap won’t make the whole PC modern.

I’d compare the total cost of replacing the platform with a used office desktop, not just the price of one upgrade. An older system with a newer processor and more memory may feel much faster in everyday use, and it can be a better starting point if the price is reasonable.

That advice depends heavily on your area, though. If used systems are scarce or expensive where you are, a modest compatible GPU might be the more practical first step.

The cheapest useful change may be adding RAM, if the board supports it and you can get compatible DDR3 cheaply. Four gigabytes is restrictive for general use. A SATA SSD could also make booting and loading feel much less sluggish, though it won’t raise game frame rates much.

Those are quality-of-life fixes, not a substitute for a newer CPU and graphics card. I wouldn’t spend much on a faster Core 2 Quad unless you’ve confirmed the motherboard supports it and the part is nearly free.

There’s a limit to how far this platform can go. A stronger used GPU can help, but it may be held back by the processor, and a high-end card would be poor value here. If your goal is newer games rather than keeping this machine usable, saving toward a newer CPU, motherboard, and RAM is probably the more sensible plan.