I don't know what "Phalaenopsis" are (appearantly some sort of Orchid), but the bottom line is - you're talking about spending $3. a gallon for "un-nuted" potting mix!
FoxFarm Ocean Forest is some of best (and most expensive) shit out there - and it doesn't cost anywhere near that much. And, by the way, 8 quarts will barely be enough to get you started!
Save yourself a ton of money and mix-up your own soil. Here is an easy recipe for beginners; all ingredients should be store bought, in bags, and are available just about everywhere:
Four-way Mix
1 equal part Compost
1 equal part Top Soil
1 equal part Perlite (and/or Vermiculite)
1 equal part "Composted Steer Manure"
Store bought "TopSoil" IS NOT the same same stuff you dig out of your back yard!