I'll have to agree with the others: Selling away your RPG books might not be the best problem:
Judging by that list, you're not just a guy who plays the occasional game to pass the time. Selling them off might not be the best idea, because chances are you'll want to use them again. It's not unlikely that you won't get that much for it, and might later want it back, going on a wild goose chase.
It might be considered quite romantic to give away the books to buy her a ring, but you'll have to ask yourself whether you won't want those books back later, and if there's a better way to get the money. Any excess organs you hardly use
That having been said, I do think you could do some "spring cleaning": Books you bought but were not that happy with, books you already read, probably won't read again, and never, ever use in your games. Books that hold no sentimental value for you. If you think about keeping something, keep it. Don't even think about it until the rest is gone (or has proven unsellable) and you still need some dosh.
On another note: I would be interested in some of the books, but since we're probably on different continents (I'm from Germany, and I guess you're in the U.S.), and the shipping would mean that I'd pay too much for the books and/or you'd get too little.