If you need, or want, to add actinics, don't waste your money on T5s. Go with VHO T12s. The generic 65w PC actinic on my 29 gallon puts out more blur than several 54w T5 actinics I've tried.
If I were doing a 90 gal, I'd go with 2 - 25w 10K MH and 2 - T12 VHO actinics.