Buy for $1200.
Take the 980 TI out: $600ish
Take the I7 6700k out: $375ish
2TB HD: $50-60
Scrap the rest (about what it's worth) Well the 7-1 card reader isn't bad to have around.
500w PS?... pass
DDR4-2133... pass
HP brand MB... pass.
SLI capable? see above.
Overclockable? See above.
Buy real components with the two saved items, spend more than I would if I just built it outright..

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@Zombiesworld: you can't pick just any MB off pcpartpicker and remotely compare it to the one in the envy... i would assume the most basic Z170 MB out there has more features than the HP branded one..
And I don't know what brand the 980Ti is either.. does HP even say? or is it an actual Nvidia branded one? (a TON of companies make "Nvidia"graphics cards... and they are not all equal) An EVGA for example is better than "Joe Blow's Super OC" from Joe Blow corp.
As far as building/buying a PC right now, there are GPU's supposedly on the way.. AMD *may* bring a new CPU out in the next year.. but they have been lagging behind Intel recently. Intel just dropped the I7 6700k.. so there *may* be a faster CPU come out eventually as well, but probably later rather than sooner. Anyone building now with a Z170 MB would still be able to just replace the CPU with the new one anyway, not like they are dropping a new socket style CPU.. just possibly faster clock speed.
I'm building my new PC now based on the 6700k, but using my GTX 770 OC for now until I see whats coming with new GPU's. Every site i've read recently regarding my new build (advice/specs/benchmarks/pricing/etc) have said pretty much the same, CPU's are going to be the same for a while, new GPU's may be coming soon. (soon as in this year)
Not a bad deal if you need a "gaming" PC and do *NOT* want to build one yourself. (Not trying to dissuade anyone from buying) But if you don't have any problem with building one yourself, you can do better.