I have the 27 watt desk lamp from HD and yes it's a 6700k.I get pretty good results from it but I did modify it due to lack of any reflector. I cut the backing from behind the bulb but left the top part of the light clip intact. I then cut a piece of thin cardboard from a coors light 12 pack and glued some mylar to it and fit it behind the bulb, it works well...
I am curious to see how much difference in growth with the 200 dollar ADA light compared to the 20 dollar HD light.
Any one have 2 nano tanks with the same substrate plants and with both lights? LOL!
There's a clipon 6700k light (think it's 13w, might be 18w) from www.aquaticeco.com. I've been wanting to check it out but can't find anything else I want to buy from that site and don't want to get dinged on the minimum purchase fee along with S&H, so I haven't bought it yet. Could work well for what you want to do though.