If you are planning for the future somewhat, go for a DX12 compatible setup, other than that make sure you have plenty of RAM.
Honestly $1000 would really buy you the lower end for computing. I look at it this way as a car that you use for work everyday. If you have to drive 100 miles to work each day, and you buy the car that drives 20 miles an hour instead of 50 mph, then you are wasting alot of time that could be used at work instead of waiting to get to work.
Over a year or two, how much time is spent saved splurging for a little better system far outweighs the cost of your time. Sorry for my terrible analogy!
Enjoy your gamedev!