That is the best advice by far
I often slow down the negotiation process....
Engage the client, tell him he has an interesting offer worth considering and you need a day or so to do your research. See if he engages you again and get a phone number. Once you have any offer over 5k you should be engaging the client so nobody gets offended or misunderstood. I usually ask for a phone number and in most cases I will base my decision on the live interaction.
That is the same way I handle my acquisitions, I always end up on the phone and that is where I do 90% of my business. A lot can be misread in an email by either party.
@usernamex is bang on..... slow it down..... I will add..... engage the client