That receiver is fine, don't pay a dime more for the electronics than you need to because it makes diddly difference. Klipsch RP are not hard-to-drive speakers by any stretch.
Skip any "upfiring Atmos" speakers --- pure marketing rubbish, they are useless. Best Atmos options: in-ceiling, on-ceiling, followed by "height" speakers.
Your sub does NOT EVER need to be from the same brand as the speakers. Speaker companies generally make mediocre subs.
Much better bang for your buck would be to hit Crutchfield.com and get their current specials on the RP series, with $75/pr flat rate return shipping for towers and $10/pr for everything else.
- RP-450C center, $400
- RP-280F towers, $800/pr
- RP-160M surrounds, $375/pr
- RP-400M for Atmos height speakers, $274/pr
For the subs, get a pair of SVS PB1000 Pro, $1200 shipped and with free return shipping.