Impreza:
Well I don't know how much help I can be in your dilema, but I will give you my two cents worth
For starters you have a 20gl tank, so you don't need to overkill with too much light. Your right, you definetley don't need to run MH on your tank.
There has been so much debate on lighting over the years-just as much or more than wether to skim or not to skim.
I have a 27gl reef that houses around 70% LPS corals, the rest of the corals are SPS. I do keep an anemone as well as a few softies too.
Over the last six years of reefing I have learned a lot, and still learning lots.
My canopy houses 3 NO tubes which consist of two Philips T3 actinics and one 10,000K daylight tube. To break this down further, I have 33gls total water volume with sump included. So if you do the math I sit at 2.7 watts per gallon. This is done by dividing the total number of watts by the volume of water. My lighting output is below standard minimum tank recomendations, as the standard sits between 3-7 watts per gallon depending on what you are keeping. I should also mention that my reef is only 16 inches in height, so not much light is needed to penetrate my shallow reef.
Over the years I can't count how many times I have thought about upgrading to more intense systems such as VHO or PCF. Everytime I thought of doing an upgrade I would sit down and stare at the reef to see if anything was suffering from lack of light, and the same thought came to mind-"if it's not broken don't fix it".
IMO I would suggest PCF as they run well, provide a decent amount of light for a tank your size, and are cost efficient. I think VHO's would be too much for your setup, taking into account what you plan to keep. The NO setups are cheaper also, but for a few bucks more you can run two or three PCF's instead of 3 or 4 No tubes.
Over this last year I have been introducing the odd small SPS frags, and to my amazment they are all not only living but also growing too. I can say
that the corals would grow even faster under more intense lighting, however this is not a major concern as I have a small reef setup. I even fragged about 40-50 pieces of coral a few months back, so most corals are growing at a great rate!
If I was to upgrade to PCF, I would go with a triple stage setup in a home built canopy. I like to run 3 tubes, this way you can run dawn and dusk simulations much better. With a standard twin setup you could also do this by starting up with an actinic tube and then a few hours later with a daylight tube, and reverse for the dusk cycle.
Hamilton make a decent double tube, 55wt canopy that would work great on your setup, check out the different setups on J&L's website.
Well, I hope this helps you in some way.
It's simply my opinion on lighting, and trust me the opinions on this topic can be endless. You can see my lighting setup and reef at:
http://www3.telus.net/sumpfinfishe
cheers, Rich