Last year I decided to add an extra 450W of UV/UVB lighting, in the form of 3-160W reptile spotlights. I did so in preparation to grow Malawi, but first was able to run a side by side experiment using the same cuttings of a white widow strain.
If you wish to add approximately 20-30% more trichomes to your bud, then you may wish to look into purchasing a few. While my electric bill has suffered, the cost is off-set by the added weight upon harvest.
Note: Indica dom strains must be watched closely when using UV, as too much will degrade THC before plants are ready for harvest.
Also, if any of you still use magnetic ballasts(I do not)I hear ceramic metal halide bulbs do a nice job when mixed w/an HPS during flowering. Unfortunately they cannot be used with my digital, so stuck here with standard MH bulb.