I'd try forum networking to get some peer advice, which may not be as brilliant but at the very least it might nudge you in the right direction!
-Derek
Not as brilliant? Here?
You can pay for coverage, you can revise based on the coverage, and still not sell the script. It's harder to sell a spec feature than a novel(statistically speaking - hopefully yours will be easier than mine).
And PS: When they say they'll get your script read by producers or agents if it's a "recommend", keep in mind that's no more than 1% of scripts they cover. Don't invest money on coverage that you can't afford to kiss goodbye for good.
That doesn't necessarily mean it's a bad idea, but I've only done peer exchanges, and like to think I've learned enough that the expense isn't warranted.
Good luck, whatever you decide.