My suggestion is if you want to maximize your dollar gain, get the keys graded and sell them. It is by far the most profitable, but does take a significant investment to grade them. You could end up spending say, $2K on shipping and grading, for a return of $5K in a couple months, so $3K profit. Sell the keys raw and you're probably looking at a fifth of the graded value. I'm new to this so others can probably give you more accurate numbers, but in my research, that seems about the average difference. That is of course assuming a decent grade (increasingly important the newer the comic). Old high grade comics can earn quite a bit of money on the initial investment in grading.
The fillers, it depends on how much time you want to spend. For your Avengers for example, leaving 420 non-keys, you can try to sell them individually for a few bucks to a buck each, or take the stack to a local store and get roughly .20/book. That's probably about a hundred dollar difference, so if you were give yourself say a $20/hr rate, you would need to individually sell 420 comics in 5 hours (not likely) to break even. Unless you don't value your time at all, then you're losing about a hundo selling to the local guy.