Recommend best way to compare new speaker to known speakers?

Happy 2022 to all.  This post is seeking ideas/recommended best way to compare a new center channel speaker—Arendal 1723 THX Center—to several speakers already here.  Arendal shipment arrives tomorrow and includes one of their subwoofers.  If the center is what I hope, buying two of the identical (except for badging) 1723 THX Monitor for main L + R is a possibility.

I want to compare the new speaker to the following to get confidence in its intended use, plus confidence in whether to buy two more: 

• my existing "theater" Center, 
• my existing theater L / R, plus 
• two or three other speaker models that I have or can readily “borrow”  (most of these are in use in 70s vintage systems)  

Actually, I’m stressing over a competent way to get the best out of this listening / evaluating during the trial period.  I will only have a single of the new speaker and it is rated 4 ohms but all others for comparison are rated 8 ohms.  If I were trying a pair, I might test them that way but there is something pure about 1-on-1 comparisons.  I wouldn’t want to mislead myself or do anything problematic during hookups and testing!  (I can't remember ever hooking up mixed rated impedance speakers at same time)

I know my testing should use familiar music in a mono source (or combined into a single channel).  I have the mono Buffalo Springfield CDs for one if nothing better comes to mind, but have plenty of streaming and local options now that I think.

It may be easier to do all the comparisons on one of my other systems.  No matter exactly how I do this, some of the speakers will be heard on systems that I normally don’t hear them on.  So I may try some approach that doesn’t overwhelm this 66 year-old body.  There are interesting ideas and discussions here so your ideas and recommendations are sure to be helpful.

Thank you.  Best Regards,

Warren