Rear channel help

Please help with my inability to decide anything. Im going to expand my livingroom setup from standard 2.1 to a 4.1 my room is big. Roughly 18x 25 ft with around a 30 foot vaulted ceiling.
I sit about 16 feet or so into the room leaving around 10 feet behind for rear speakers. I need to mount them high and position downward. Sliding glass door and furniture in the way. Im overwhelmed with choices. Die pole. Traditional. Even going with convienent outdoor rated speakers that have directional mounts included. Any advice is appreciated. Current set up is an old adcom gfa555ii amp. Fronts are a stable of sometimes jbl 590s. Heresey. Pioneer hpm100s. And occasionaly magnapan mmgs. Thanks

so are you trying to do stereo, but with fronts and backs that are paired?

No. A 4.1 surround for movies

And yes the adcom is 2 channel. More amps are not a concern. And yes i have a 7.1 processor already. Just looking for driver advice

The general idea or ideal option for surround sound would be to have speakers from same series or lineup as the rest of speakers. Same drivers, same tweeters and so on.
That way the sound signature is the same. Sounds and effects sound the same.

So if you have JBL 950s, high position mounting so probably only similar speaker would be JBL 530 for rear surround.

As a extreme example.
You would have 590’s as front speaker and small Polk Audio speakers for rears.
If the movie / series has a effect that goes front to back or spins from front left to rear left and so on. You will hear the sound signature changing, the effect sounds different while moving around.
Or any music effect that moves.
It sounds weird at the end if you generally notice sounds changes and different driver tuning.
Similar if you would have JBL studio as front left speaker and Polk audio as right speaker.
If you would not notice anything… then anything you can find and can mount is good.

Spot on with the post. I will pick something soon. Svs and other companies are selling… i guess theure bluetooh units to take the place of rca runs. Im not an experienced wireless tech guy. Curious about powered bookselves. The problem that clouds my head is how…or maybe im answering it for myself… an svs wireless module for my emotiva mc700 rear outs and into the powered bookshelves analog in??? Mc 700 should still be controlling volume levels. Just set the levels on bookshelves untill proper balance is found for volumes. Then never touch the knob again. Or untill i get drunk and insist that drunk steve knows best.