XPS 8700, upgrades?

Upgrade RAM, CPU, Drive, GPU, PSU, etc.? Could you be slightly more specific?

Options: cpu to i7-4770 or 4790.

ram to 16 gB (4x4 GB)

gpu to discrete video card depending on your budget

(psu may or may not need upgrade)

if you have mSATA or hdd only, upgrade to 2.5 sata ssd.

Finally, if you wish to keep the case only and upgrade entire motherboard, any standard microATX mobo will fit n work in this case.  so in theory you can install an Intel 500 series mATX board w 10/11th Gen cpu, which is a quantum leap from the stock Z87 chipset and 4th Gen cpu of 8700.