Speaker static/hiss?

Your speakers have slightly higher than average sensitivity. A21+ is a good amp that looks like a reasonable pairing here. That Marantz though - a 13.2 channel preamp? Holy cow! That thing is so chock full of multi-channel features they don’t even bother to list a gain spec. But that would be the most suspect component here. Maybe it has a variable or selectable gain feature you could play with? But really, the easiest solution should be to lower the gain pots on your A21+ until you reach a good balance. You're lucky to have an amp with that feature - most modern hifi amps don't (some of us get antsy about extra potentiometers in the signal path - same with balance controls). What do you currently have those adjusted to? Are they at max gain?

Nothing to worry about. I had a amp that did the same thing.

When no source but equipment is turned on is there still a hiss? I use a pc for my source with an asus essence stx ii 7.1 sound card with crown xls 1502 and 2502 along with an xti 6002 and two cerwin vega subs one being a cvx-21s and an el36dp, my speakers and only the cvx-21s when turned all the way up no hiss or sound if my pc is turned off. I'm not sure about the el36db i've never tested that yet but when i turn the gain all the way up it rumbles a little. Now when my pc is turned on even with the gain low the tweeters make a hiss noise up close while the cvx-21s no audiable noise except what it's suppose to be playing. So if there is no hiss when source is turned off it's the source itself that is causing the hiss, if it's a grounding problem it hums not hisses, it's normal for tweeters to hiss since they play so high but don't worry when being used that hiss is unheard at a decent volume level.

Do you have a tube ,amp, or preamp ? That’s most likely the culprit.

Suboptimal gain structure FTW. Somebody has some pro audio experience and a good mentor. I had both and the two key lessons I learned about signal chain were grounding (hum) and gain structure (noise and headroom). And both are seriously ignored in most hifi systems. If either are problematic in your system, the fix is to properly set your system up, not shop for new pieces that happen to match your system needs.