i have had alot of success with pc's over the years. Ive grown everything from softeis to sps under them. If your running a 20 gallon tank, twin 65's in my opinion are fine. If you were trying to grow strictly sps or clams you may need halide but for a starter reef i dont think you need waste money on any other lights. Just make sure that you know what requirements your corals need, if they are more light demanding put them closer to the surface, the ones that dont need high lighting or current keep in the middle or on the bottom. I ran a 55 for a long time with only pc's and had a very nice looking tank without the worries of overheating, electric bills and all the other stuff that goes along with halides on a small tank. Also if you want more juice from your bulbs use only 10k's instead of one 10k and one actinic. I would recomend starting with some mushrooms, any type of leathers, clove polyps or zoanthids. All these should do well under pc's and are fairly easy to care for. Also look into some type of dosing chemical for your tank, for a small reef like that i think b-ionic would work well. Its a 2 part daily dosing chemical that is sold in any decent reef shop. Good luck with everything.-Mike