Is the RTX 5080 worth paying CAD 700 more than the RTX 5070 Ti?

For most buyers, the RTX 5070 Ti has the stronger price-to-performance ratio. The 5080 is more appropriate if you want maximum 4K settings, higher ray-tracing performance, or a longer comfort margin, but it may be overkill for your current 1080p setup and CPU-heavy games. I’d take the first build, verify the used drives carefully, update the motherboard BIOS, and spend the remaining money on a good 4K monitor.

The 5070 Ti system looks like the better value. The 5080 will certainly perform better, especially at 4K, but the improvement probably doesn’t justify another CAD 700 by itself. Since you still need a 4K monitor, putting that money toward the display may give you a more noticeable overall upgrade. The 5070 Ti should be a reasonable 4K card when using sensible settings and upscaling, although nobody can say exactly how GTA 6 will run on PC until its requirements are known.

The first system also makes more sense for your games. World of Warcraft and Cities: Skylines are usually more CPU-limited than GPU-limited, so the 5080 won’t always provide a major benefit. The 9800X3D is already an excellent gaming CPU, while the 9850X3D’s extra performance may be fairly small for the additional heat and power draw. Likewise, an X870E board is mostly worthwhile if you specifically need its extra connectivity or expansion features; a good B650E board should be fine for a normal gaming build and future upgrades.

The used storage is the biggest concern with the cheaper build. Check its health, power-on hours, and total written data before relying on it, and don’t treat the builder’s reputation as a substitute for a warranty on those parts. Since you already have a 1TB SSD to add, the 4TB advantage is less important, but the lack of warranty still has to be reflected in the price. If the used parts test well, I’d choose the 5070 Ti build; if the warranty and peace of mind matter more, the 5080 system is the safer purchase.