Ya...,in the end double-tracking a vocal hands-down really thickens the performance up, especially if you take time to align the 2 together. I would sing it twice, comp 2 good vocal tracks, align them, and then put the best one 5-6 db above the other. Carve out around 5khz 3-4 db on the "backing" track with a moderate bandwidth, and boost around this area on the track up front. You could also go a step further by cutting 3khz 1 -3db on the up front track and simultaneously boosting 3khz slightly on the backing track with a small bandwidth, (Q of 2.0 - 2.8).