Question on home theater/music listening set up

Hey all! I am new to the forums. I was introduced by another member here and I have to say I am blown away by the amount of information on here. 

My question lies in the 7.1/7.2 surround sound systems. I will utilize my setup to watch movies, tv, and when I have the house to myself I love to put on some older 80's rock and sit and enjoy the setup. I love to dabble in classical music and for some strange reason I love horns. I am a big lord of the rings and game of thrones fan, and during battle scenes with drums, horns, ect I want to feel it in my soul haha. I love what I currently have, but I am trying to polish out what I have. I am open to suggestions on any brands that may go well with what I have now. My price point is primarily the used market. If you could just suggest the speakers you think would compliment the system I can attempt to find the best deal on those as possible. 

My current setup is as follows:

Polk Audio SDA-1A
Polk Audio SDA-2
Velodyne Minivee 8
Monitor Audio MR center channel

Denon AVR-3803

Power Conditioner-
Belkin AP41300-10

I have looked into ELAC, B&W, MIRAGE, PARADIGM, SVS, Ect trying to find something I like and I finally figured I should open it up to you amazing individuals to lend me a hand. 

Thank you in advance!
I just added an Anthem 520 to my 5.1 and it’s a huge upgrade.  Their room correction software is great and it sounds so much more immersive.
Someone I know 😉 has a ATC 5.1 speaker package for sale on AGon and also has a great amp and processor that can be added for a reasonable price 😂. You can take it up to 11.2 and includes room correction.

just saying 

My 2cents FWIW, them old Polk SDAs are awesome for their age.  They will blow many away with their soundstage. That said, they really can be improved upon by a relatively low expense room treatment and optimization. Why do I say this? My HT system was set up around vintage Polk. SRS-SDA 3.1TL,  CS350LS,  FX500I. A subwoofer will really help here. After room treatment I was IN and part of the action on the screen. Used it for both HT and 2Ch and never regretted the cost of the treatment. Just sayin!