Location...Location..Location!!!! Help is required

If you place your seating at one of the 1/3rd or 1/5th divisions of the room length, it will help give you smoother frequency response (fewer and/or smaller peaks and dips). For your room, I would place the first row around 9.25 feet from the front wall (2/5th point) and the back row about 7.75 feet from the back wall, which leaves a comfortable 6 feet between the rows for people in the back to stretch out their feet or recline. At your current 11 foot distance, you're near the middle of the room, which will result in greater swings in the frequency response. Also, at that distance, a 65-inch TV is going to occupy a tiny 24 degrees of viewing angle. Not very immersive. At 9.25 feet, you're almost at 29 degrees, for a bit more immersion.

To get a nice wide soundstage I would spread your front speakers about 12 feet apart and mount the centre speaker so that its tweeter is the same height as the ones in the L/R floorstanders. If you are willing to mount the centre speaker vertically, then that would really help listeners on either end of the rows. Horizontal woofer-tweeter-woofer designs typically sound bad off-axis.

In your drawing, the sides and rears are close enough in angle that it will almost sound like a 5.1 set-up from the first row. Mounting your Polks surrounds directly to the sides of the first row will help stabilize lateral imaging AND give you good rear-vs-side separation in the surround field (one of the hallmarks of a 7.1 set-up). Set the bipole/dipole switch to bipole, for more even coverage across the seating area. For the moment, mount your JVC speakers in the back corners of the room, with the back of the speaker stradling the corner. Hopefully you'll replace them with another pair of F/XiA4 surrounds down the road. Mounting the surrounds about 3 feet above seated ear level will help improve envelopment and provide a bit of height imaging (not to mention keeping your guests from bumping their heads on the surrounds).

Finally, when you get ready to replace your Sony subwoofer, consider getting two. Placing them at the midpoints of opposite walls will give you better bass consistency from seat to seat. That makes it easier for room correction systems built into receivers to do a better job fixing problems across multiple seats, since the subwoofer placement has made problems more similar across multiple seats.

You're welcome. If any part of my post didn't make sense, just ask and I'll try to clarify.