Don't put much stock in EPC numbers provided by networks. You have no way to know how those numbers are derived or what the people who contributed to them did to get them.
The only way to do it is to test for yourself. It sounds like you are looking for a quick fix to get your 8k back.
For you to learn what you need to now to realistically turn that 8k into 20k would probably take more than 2-3 months unless you were extremely lucky. I say get the check and go for it.
It does not sound to me like you have the patience to actually do what it will take to use that money successfully which likely means in a few weeks to a month you will have CJ send you like 1500 and that will be that.
You are of the ignorant believe that Affiliate Marketing is somehow easy or an easy way to turn cash into more money. If it were so easy don't you think even more people would be doing it? It takes a lot of work and most people who try to do it fail.
People with experience could put your money to good use, although I honestly don't know of many good affiliate marketers who have cash flow issues, so probably not. The reality is it can be hard to find enough to do with the money they already have, so more money is of little use.
Again, just get the check and put it towards something you are experienced with... If you really do want to learn affiliate marketing, have them send you a check for 7500 and keep the other 500 to play with... Do as Rhino said and set up a test for $100.00 to start with...
One thing you have to understand about the affiliate business is it is a really boon for the companies doing it. They have little to no risk and pay out, for the most part when they get revenue in or an expectation of revenue. Many affiliate programs can be amazingly difficult to find and match up an audience with that can convert. As MadeWillis said, nobody who has actually invested the time and money to find those out is going to share it with you. It is worth a lot more to them. You will find some shills pushing offers or categories, but these are almost always after something has peaked and they have moved on. So you are not going to get any hot leads.
I have run on long enough.