I don't think it is as simple as "1-2k" or "3-5k" and that is it. It is one thing to come up with a reseller value, but trying to figure out what an end-user is willing to pay at the start of negotiations is sometimes a shot in the dark.
Do you know who the buyer is? A search for these initials brings up a very large company (listed on the Nasdaq) that prominently features their "charities" on their website. This Charities branch is a non-profit that doesn't really seem to have a site of it's own except a Blogspot page, but it apparently has good funding. If it is in fact this organization you are in a pretty good position.
If it were me I would start at $9600, and see what they come back with. I would justify the price using the facts that it is a 3-letter domain, that it is so old, and that it is a PR6 which will help it be prominent in search results (these ARE impressive facts).
I like to say something like "please let me know if this price sounds fair to you" which is non-threatening and can leave the door open for them to counter. If they are already thinking in the low $x,xxx range this shouldn't really scare them of. If you don't hear back you can always follow up a week or so later and invite them to make an offer of what they think is a fair value for the name and see what they say.
It really all comes down to getting that response and trying to gauge their reaction. Also, try to determine who they are and what their plans are for the name. From there you can use this additional information to determine the maximum that you think you can get.
I think $2000 is the low end to expect from an end user, and imo you would probably be getting the short end of the stick. $5000 would be good, and based on how they react to your quote you might be able to shoot for $7500 to $8000.
You have to ask for it to get it. If they aren't serious and you scare them off, oh well... You still have your name and there is always tomorrow.
Sorry for the long reply to a short question, but I have had many end users contact me like this over the years and I have thought about these things quite a bit. I actually got an offer from an end-user today myself (pretty low offer, but it is from a muti-million dollar corporation so we will see :smilewinkgrin
Good luck and let us know how it goes!