Obviously you'll end up with a better set of speakers if you spend the $1000 on the front pair first and then add the rest of the comparable matching speakers later.
The only caveat would be that if timbre matching is important (which it should be, at least for the center) that you do not wait too long to purchase the additional speakers as you may find that the exact matching speakers are no longer made by the manufacturer. So, plan ahead as best as possible.
"All men are frauds. The only difference between them is that some admit it. I myself deny it."