Where to place the speakers?

[Gremlin]

From what the seller at the store told me it wasn't as important with these as ordinary speakers.

Unfortunately that statement is not quite right and must be labelled as a 'convenience' for the seller. In this context Phantoms behave mostly  like any speaker. Only speakers that have built in correction features for asymmetric placements, such as the Kiis, can be described like that.
I am sure you'll find out of it - good luck!

I think it's worth adding that the Kii's cardioid radiation also helps to greatly reduce room problems.

The Dutch&Dutch 8c is also worth considering, also cardiod and individually adjustable.