Vintage and modern hookups

It’s a 60s unit. 4 watts a side. RCA speaker connections. Sure you can use it. Hopefully the input won't overload with the high output from CD/DVD. Feed CD or PC audio into the tape input and make up speaker leads with RCA plugs making sure not to short the wires.
Don’t over drive it or you could damage the Polks with distortion or worse.
Hope you didn’t pay much for it though!

Far as I can tell it's a Denon solid state AM/FM multiplex am/FM MX-990 A! I'm wanting to hook up my Polk Audio surround sound speakers with an Energy 8 in. Powered sub! 

I used a Phillips RV450 Surround Processor thru the tape loop with a Sansui integrated years ago and it worked great. It has it’s own speaker terminals. There are a couple on eBay right right now for cheap. Assuming you are looking for surround sound and not just another pair of little speakers plugged into that vintage amp.

You want to connect speakers to inputs?  That must have been some of Belushi's best.

do you mean will you burn out new small surround speakers with too much power?

use them for main speakers or for dual front/rear quad type surround?  

what brand, model receiver do you have? we can look up the specs/features easily enough.

a lot of those had speaker options, A, B, or A+B.

that would let you use or not use them.

any specific surround speakers in consideration?

higher efficiency/sensitivity, 89 spl 1m/1w or higher is always beneficial, now and in the future, reduces your power needs, lets you try tube amp

Is that stoned once, or once stoned? LOL like the name, Kinda says it all "70s" receiver
some good stuff back then if you looked..Sansui, Mcintosh, Marantz.

8 ohm speakers for sure, but check on 6 or 4 ohm.
Second it will be stereo or mono if you choose.
The only part of surround will be in name only.

Probably sound just fine.. The inputs will work for LPs and pick another source if you want.. Music Channel, or CD..

Have fun

Regards