Letter from CashCall

I did the wrong thing at one time, needed money, and used Western Sky to get it. I took the loan out for $2600 about September of 2011. I was making payments until march, which by then, I paid $1519.49. My loan was of course sold off to Cash Call after the first payment. I got a few calls about the amount due for like 2 weeks after I failed to send in a payment in March, and nothing since. I keep getting letters every couple of months with them trying to modify my loan agreement, and making me pay a little less, but not much. Today I received a letter that says.
Dear
This is your opportunity to save up to approximately $10,589.20 on your CashCall loan. Currently, you have 43 monthly payments of $294.46 remaining on your loan, which adds u[ to $12,661.78. We want to resolve this matter as quickly as possible and avoid further action, so we are proposing the following settlement offer:
One lump sum of $2,072, due and payable on or before June 29, 2012. This is a 20% reduction of your current principal balance and would result in a savings of approximately $10,589.20
Or:
8 payments of $323.84, beginning June 29, 2012 and continuing on the 15th of each consecutive month. This would result in a savings of approximately $10,071.06
I was wanting to get some peoples opinions now. What further action, if any, would be taken by these dirty people. Given the fact that many assume I should just pay them the principal balance, and no more, that would be just 1080.51. Now, I don't really feel that I owe them anymore, since finding out how corrupt these things are. I wouldn't mind paying them back the rest of the balance, which would be 1080.51 or even settle on an amount less then that.
What should I do here guys? Should I just keep not making payments until they settle further, but then I don't want that further action to be bad. Or should I send a letter of my own, back with a copy of this one, and try to negotiate a settlement myself.
Any ideas on what to do?
Thanks.