I agree with wuzzzer. If you're listening to music such as techno, electronic, or certain types of rap for instance anything that dips below 30Hz, then you'll likely benefit from a subwoofer. Most other music, no.   A subwoofer is definitely needed if you're using the system for movies.   If you do play anything that reaches below the low cutoff of your main speakers, you'll definitely want electronics that will filter a high pass signal to your main speakers and protect them from over-excursion.   Ask me how I know...😉    

massive woffer Delta pro 12a ,$159  klipsch has been useing emi for years...reg 12a is all you need..lol

Recently purchased two RSX-4 surround sound speakers off FB Marketplace, but they didn’t include the mounts. I need the screws, metal plate, ball, and mount plate. 

Thanks you all, but unfortunately I have only the speakers. No metal plate, screws, mount, or swivel. I need all of that. 

From what I’ve seen I’d say 4-5k on the Khorns, 3-3500k on the Belles and 750-1k  on the H IIs.

20k sounds perfect!!! 😀

It would depend.  If you’re listening to basic two channel music they’re probably ok on their own.  In a home theater environment or any music that’s bass heavy then a subwoofer will help out a lot.

Wow.........not in market myself but Wow. GLWYS. I'd say 4K for Ks, 1500 for Belle and 1500 for the HIIs. So 7k but hey its Cal. so 20k

I have already written about this topic a few times. I myself had Crites AA 17 years ago. Forget it. It's outrageous that Crites offers different qualities of bass coil. The original Klipsch coils are the best you can have and they will never get worse in 100 years. There is no wear and tear. Sonicaps as a feature of the most expensive version of the Crites AA are a tinny, aggressive sound. There were times up until 12 years ago when I was happy to buy other Crites products. But with today's Crites prices for fake AA xovers which are far away from the good original sound, I can only warn you. BTW your speaker can not use Type AA networks at all. Today I have to say that this AA from Crites is not a serious offer. The price of more than 800$ for a few components is a provocation.

Thanks for the suggestions! I'll clean them and see if that fixes my issue.