Most domain names you consider good now are not good because of the name, but because of what it was used for. Domain names, in and of themselves, are generally pretty worthless (unless you happen to own one of the rare few) and I think it would be much better for you to work on your sites content and then finding a suitable name after.
Besides, what use is a domain name which follows your criteria but is meaningless in the context of the product? Build the product, find it a name, name the domain something related to the product name or purpose. Save your $500 for somehting else.
Thats my opinion, at least.
Incidentally, I'm willing to part with enemynetwork.com for $500 (or an ipad) :-D