Placement of Revel Performa S30 surround speakers

The dealer is wrong on wiring them out of Phase! This is not the solution, no.
However as for set-up of the speakers, one would need to be able to see your room and set-up. EVERY room is different, and requires different considerations.
Really, there are ways to find the best placment, and it doesn't simply have to do with where someone thinks they should go! if you want the same sound balance with the front speaker, so the speakers will all dissapear acoustically, and proper coupling of them to the room/seating possition, there is quite a lot more to it than simply saying they should go here or there, based on theory! If you want anything resembling high fidelity, top caliber sound from those excellent speakers, you need to really have someone do it for you!...the possitioning that is.
Setting up speakers, for excellent results, is not a simple proceedure. it really takes knowledge, exerience, and some acquired skill to do it well, and few can do it right! THIS ARE IS WHERE 99.9% OF ALL AUDIO ENTHUSIESTS, AND EVEN LONG TIME AUDIOPHIES, SCREW UP! I've done over 1000 systems in my day, and have worked in 5 high end stores, been to all the shows, and counless homes....trust me, most people SCREW UP THE SPEAKER PLACEMENT!!!
You really should pay someone who know's what they're doing to look at your room, and figure things out for you. Unless your willing to spend years, and thousands of hours trying to figure out how to do it well, you really should consult an expert on the situation. Otherwise, what you find is that you'll highly likely get only mediocre to poor results from otherwise excellent, yet mis-installed gear!
If you doubt, just email ANY of the stereophile writers and ask em!!!...ANY!
Your Revel's, I believe, are ported speakers, correct? This usually always makes for very difficult "close to wall proximity" possitioning. Whatever you do, make sure you configure them for "small" on your pre/pro.
My dad used to say, if you need something done, you always go to the expert on the matter!!...my suggestion indeed...
Good luck

OOOOPS!....just realized you are talking about dedicated S30 surounds. I was thinking about the 20's, which are ported. These speaker(S30's) are sealed, and are balanced from the crossover to be flush against the wall. However, for proper sound, you still need to have them placed properly on the walls/ceiling/etc, whichever. Placment is still critical in the room, and require attention. If you chose to do it your self, may I suggest you pick up a lot of info on how to place speakers.
Good luck

I recently purchased a pair of the same speakers. Like you, I plan on installing them on the back wall. My take, after reading the Revel S30 manual, is that you want the speakers 20-30 degrees behind and 15 degrees above the main listening area.

If your listening area is six feet from the back wall, and assuming your ears are about 44" from the floor when you're seated and listening, then the 15 degrees higher would put the speakers at a height of 68" (44" + 24") from the floor.

I don't know that I can help with the recommended separation between speakers. I ended up with about 12 feet between the left and right surrounds.

Hope that helps. If you don't have Revel's manual, you can get it from their web site.