I'm not much better at this sort of thing than Rob is unfortunately. If it was a current generation system, or even one generation back it would be easier to give you a ballpark amount.
If this helps at all, two years ago I sold the following system for $450.
Intel i3 (can't remember the model, but it was 1st gen)
GIGABYTE H55-based mATX motherboard
4GB DDR3 1600mhz
Mushkin SATAII 80GB SSD
WD Caviar Black SATAII 500GB HDD
I don't remember what case or cooler I sold with it, and I'm pretty sure that I kept my power supply.
I'm sorry to say that the rig you listed won't be worth a whole lot, but depending on how up to speed they are on technology. Obviously you're looking for a dollar value, which I just can't give you.
One resource that you could use is the appraisals section of overclock.net
. I haven't been on that site in years, but after I sifted through the elitist bullshit that comes with hiding behind a screen name, I found tons of useful info.