Any of the modern GPUs should have compatible DisplayPort outputs. You just need to check the vendor specs of a particular model to be sure. Can't tell what motherboard the pre-built CyberPower uses, but in the picture there's a single blue colored USB port, which would indicate that it's a USB 3.0/3.1 port. If the picture is accurate to what you'd be getting, then it should work for the Valve Index.
VR is much more demanding on GPUs than non-VR titles. Check out these VR gaming benchmarks to get a better idea of how the 2060 Super performs. Based on the data, you'll definitely need to adjust various in-game and VR headset settings to hit and maintain high framerates no matter what GPU you get, so getting the fastest one you can afford to is recommended.
And if you're not strongly averse to learning how to build your own PC, I'd recommend putting your own PC together. With today's prices, you're looking at ~1000-1400 before taxes and mail-in-rebates for a 3600/3700X-based build with an RX 5700 XT, 2070 Super, or 2080 Super as the GPU.
A good 1080p/144Hz or 1440p/144Hz IPS monitor can be had for ~200-400 (when in stock), but if you don't mind a TN or VA panel, you can spend a bit less.
