Depends on the specificity of the PCR, though I have found that gel isolation in general can usually save a lot of trouble.
When isolating from gel it is important to let the collumns dry for several minutes after the ethanol/buffer wash to remove all traces of ethanol. Elute in MQ or simply ddH2O. For larger fragments, it helps to prewarm the ddH20 or MQ to about 40-50 deg. C. before applying it to the center of the column and let it sit for 2 minutes or so. Never trust nanodrop! I always check my fragment after gelisolation again on gel.