What Watt HPS/MH Should I Use?

lol I know, this HPS system is the already the result of wanting to do more. I've done several CFL grows with an AeroGarden. I'm thrilled to be on the HID side of things now! I'm going to probly go ahead of do a400w grow my 1 seedling is barely above the surface of rockwool and im planting a germinated seed in rockwool tonight. Thanks guys!!

It's all good, lol I was blown away at first.