I'd say go with 85 or 105 watt CFLs if you're growing 4 plants. I like to use 6 per plant but in your case you would probably be good with around 8 85 watt daylight whites and 8 85 watt soft whites. That equals 1,360 watts and about 134,000 lumens which would be great for 4 plants to really thrive. The more lights the better the yield but when you're talking about a lot of CFLs, eventually it gets to a number where it's probably smarter to just invest in a nice 600 watt or 1000 watt HPS or MH light instead.