Lycaste aromatica is a great species... actually that whole section (including Lyc. consobrina, Lyc. cochleata, and a few others) is great - the flowers often appear before the new growth even starts. Which makes for a great display because it doesn't get marred by ratty leaves.
For Lyc. powellii, have you checked
Andy's Orchids? If it's not on the website ask anyway, the website shows only a small fraction of what he has. If you can't find that one, consider Lyc. dowiana, or Lyc. deppei ssp. praestans (the latter I have from Andy)