I used double the amount of k-sorb to stabilize my 1 gallon batch of peach wine. Should that have much of an affect on taste? I don't think I need to pitch the whole batch.
While the extra sorbate wasn't needed, it won't ruin the peach. According to Tim Vandergrift of WinExpert most people can't even detect the sorbate, so it should be fine. You still are in a safe range.