You don't quite need that powerful of a CPU and graphics card, though they're good choices for VR if you can afford them (they hit the recommended Oculus specs rather than the minimum requirements).
Upgrading these Dell prebuilts can be a little tricky.
For the CPU, it... should work with other Skylake chips. On paper Kaby Lake ought to work too with a BIOS update, but Dell will likely have skipped that kind of update.
For the GPU, there are two things to worry about - one, will it physically fit inside the case (pretty easy to check), and two, is the power supply going to support it or can you upgrade to a compatible power supply. You can check the PSU ratings, should have a sticker on the side of it, or you can check if it has the necessary PCIe power connectors. Chances are it doesn't, and then the question is whether a replacement PSU would fit inside the case, and whether the motherboard uses standard power connectors. There should be a 24-pin (or 20+4-pin) connector and either a 4-pin or 8-pin connector. If the 24-pin is segmented in some other way than 20+4, that's the most common sign that it can't be upgraded.