No you do not have to stay brand specific.
I have
Faital 10's
Beyma 8's
Faital 6.5's
Gz 6.5's
Gz horns

You need to research a speaker that will work well with your perameters. U.S speakers website is a wealth of knowledge.

I would rta your system and see where you are missing the frequencies at head level on the bike.

This will also tell you how high/dB volume your system is and will help pick a speaker to compliment the system.

Looking at the graph of those speakers, there are some choices in the beyma line. But, come up with a realistic budget for gear and I would include a good 8 channel DSP.

Look at these;
http://www.usspeaker.com/beyma%208wrs300-1.htm

Juice

 

Here a a price friendly option, just spray it with camp dry a few times. They do not need as much power either.


Juice

 

I thought the CVO was twin cooled. If so then I have not been able to find lowers that fit an 8” speaker.

 

Wet head not withstanding, the crash bar hasn't changed in 30 years. My 17 SG has eBay'd early model Harley OEM lowers that I had for my 03. BTW, If your painting, I bought Harley OEM speaker pods for about $10 more than the eBay generic pods.

 

U absolutely don't need to match brands. U need to determine exactly what ur missing or trying to obtain from the platforms and chase it via the best damn bang fir the buck possible. Euphoria at 2X their actual value is something I would not chase.
Tons of very nice 8s fir lowers. Maybe start by looking at the two different Hertz 8s and compare stats for ur riding style the start narrowing product selection based on that initial assessment.

T

 

Because the CVO has the small engine guard, pretty sure I will have to go to the large standard engine guard. I am going to the shop today to find out if the engine guard can be changed out. I think that is the only way to add lowers with the 8's. Talking to Lucky 7 the Dirty bird lowers and paint you're already 1K in. I just don't see putting money into sound that is not up front. Little of my commute each day is below 60mph.