Well you have created something of a dilemma for responders to your post. You have essentially said, what can I do with what I have, and limiting it to what you have, the only response can be ... use what you have.
The Klipsch RF-82
($370) are not exactly pixie speaker, they have TWO 8' bass drivers, meaning they move considerable air.
The Power Sound Audio CXS-30 Sub
is equally not slouch - 15" driver, response flat to 19 hz, 130 spl, 725w amps -
The Klipsch RC-62 Center ($350)
. The Center has TWO 6.5" bass drivers, that's about as big as a Center can get. I don't think I've seen any 2x8" Center speakers.
The Klipsch RS-52 ($299)
are specifically Di/Bi-Pole Surround speakers -
So, the only question that needs to be asked now is ... do you like Klipsch?
I keep auditioning Klipsch at Best Buy, but they are not in the Magonlia audition rooms, they are on on the main floor stuck between two narrow isles. The Main Floor has a stunningly high ambient noise level, and the Klipsch really cut through it. Other similarly price speakers sound very recessed in all that noise clutter.
So, I suspect the Klipsch could to an amazing job for movies, given their price, but I suspect if the room is overly bright, the Klipsch could become overbearing. If you are building a true Home Cinema, they you definitely want to soften the room considerably.
If you like the Klipsch and you have limited money to throw around, I would be inclined to say an AVR upgrade tops the list.
The Pioneer 1121 Receiver
seems to be somewhat middle of the road, last selling for $550. I think you would do better with a new AVR in say the $750 to $1000 range. Though you might find some bargains a the end of line.
Here is an example of bargains that can be frequently found. Here is a highly rated $1600 amp for the low price of $799 -
Now as to moving to 7.1 or 9.1, that all hinges on the room.
We would need DETAILS on the room this will all be placed in. There is little point in moving to 7.1 in a small room. And even less point in moving to 9.1 in a less than ideal room considering there are no 9.1 sound tracks. All those extra channels are synthesized by electronic magic.
So, we need to know the details of the room? The Dimensions? A general description of the room so we can get some sense of the acoustics. The nature of the room, IE: Living room, dedicate home theater room, etc...? Where is the furniture place? Carpets? Curtain? Etc...?
Then most important of all, how much do you have to spend to make this upgrade. If you don't have money to burn, then no point in proceeding.
Logically, if you expand to 7.1, then it become a matter of Di/Bi-Pole
like your existing Surround speaker, or Direct speakers
like bookshelf. That's about the only decision you have to make, and that decision is based entirely on what is possible in your specific room. With out clear details on the Room, your guess is as good as anyone's.