I'm running a glass Versa-top on my 20H with a pair of 8.5" diameter clamp lights and (believe it or not) 9W 6500K CFL bulbs in each. Substrate is pool filter sand (tank is all corydoras and a BN pleco) and plants are a mix of the usual low-tech stuff including a melon, ruffle and narrow leaf sword. Root tabs take care of those and a dwarf sag, Flourish and Leaf Zone for the anubias and ferns and a few crypts.
I went with only 9W bulbs to start out after seeing how effective these reflectors were at delivering light to the substrate from the data posted elsewhere on here. I'm not running CO2 or Excel, so no sense going nuts on the PAR. Plants are definitely growing, although I think I'll need to rearrange a few to get the higher light needs plants more towards the center under the lights or move up to 13W bulbs and raise the lights up 3 or 4" to spread out the coverage a little more. The 9W lamps are so small that their "light center" is far up in the reflectors which tends to focus the beam more tightly compared to a big 23W lamp that sticks out almost to the edge.
The only thing I don't like is I have to move the lights whenever I need to open the lid whereas a strip-style light would work just like a stock unit. But, the FEIT 6500K lamps dp give a very nice color rendering to the tank without the "fake" bluish look that some LED's give off.
Chris