Autoformer vs Speaker impedance Curve

@73max

Your B&W 802 D3 will be better off driven by a pair of Classe Delta CAM-300 monoblock amps or the CAM-600 monoblock amps. I’ve heard these B&W 802 D3 paired with the Classe Delta CAM-300 & CAM-600 monoblock amps before as well as the Mac MC601 monoblock amps in the same setup and same listening room environment.
They sounded best driven by either the Classe Delta CAM-300 or CAM-600 monoblock amps. These Classe Delta series amps have been discontinued last year and can be had at discounted prices if you can find a used pairs.
The Classe CAM-600 originally retail for the same price as the Mac MC601 ($14k/pair) and the CAM-300 originally retail for $11k/pair). 

These B&W 800 series D3 speakers pair really well with Classe Delta series amplifiers. They sounded great together.
I’m currently using the Classe Delta CAM-600 monoblock amps to drive my B&W 800 D3 front speakers in my dedicated home theater room. They sounded spectacular together.
I’m also using the Classe CAM-300 monoblock amp (single) to power the matching B&W HTML1 D3 center channel speaker. Classe and B&W have great synergy together.

With your B&W 802 D3, you will be better off keeping your Classe CA-2300 or upgrade to Classe CAM-300 monoblock amps or the CAM-600 monoblock amps rather than getting the Mac MC601. 

Try and have a listen to the Classe CAM-600 monoblock amps on your B&W 802 D3. The Classe CAM-600 is a step up from and is in different league than your Classe CA-2300 or the CAM-300. Not only the CAM 600 have twice as much power than the CA-2300 or the CAM-300 but the CAM-600 sounded and perform better, quieter, more musical and better separation and better image focus much more dynamics better slams larger wider deeper soubdstsge better image depths and better overall more refined sounding than the CA-2300. The CAM 600 can also do subtlety better than the CA-2300. The music has more presence with the CAM 600. The CA-2300 is great but the CAM 600 does everything more and better. 
They will sound really good on your B&W 802 D3. 

I'm myself using the Classe CAM-600 monoblock amps driving the B&W 800 D3 in my dedicated home theater room with the Classe SSP 800 as my AV preamp surround processor. I use this setup strictly for home theater (bluray & 4k UHD disc playbacks from my Oppo 205). 
I didn't find the fan annoying at all. It was hardly audible even when it's on when no music or sound is playing. Depending on how far back your listening position is from the amp(s). You might want to check and see if the fan filter needs to get cleaned. 

As you might already know that all Classe Delta series gears, which include the CA-2300, CAM-300, CAM-600, CA-5300, CP 800, SSP 800, CA-D200, have been discontinued last year and nowaday can be had at discounts. The CAM-600 originally retail for $14k/pair and you can find a used one for probably less than $10k/pair. 

Or alternatively, the Classe Omega monoblock amps are even better sounding amps than the CAM 600 and all other Delta series amps but the Omega series gears are older than the CAM 600. I think the Omega monobloclosed amps were discontinued like 10 yrs ago. They were first introduced around 2001/2002 I think. If you can find a used Omega monoblock amps in mint excellent condition and make sure all the caps are still good or have been replaced with Classe original ones I think you should not be hesitant to grab them. They are excellent amps. 

In regards to class D amps, as suggested earlier by Georgehifi, Bel Canto, Theta, NAD Master Series, Classe Sigma series amps all make excellent sounding class D amps. They aren't my favorite amps. I'm more of class A or AB or valves kind of guy. Actually I had listened to the Classe Sigma Mono Amps monoblock amps (class D design) paired with the B&W 802 D3 before at a local dealer here and I thought they sounded great together but I prefer the analog class A/AB amps from Classe such as the CAM 600, CAM 300, CA-2300 or the Classe Omega series amps. But the Classe Sigma series amps are very good considering they are class D designs. 
Classe uses its own proprietary design in designing its class D amps with the Sigma series amps. 

I personally have never heard Pass XA-160.8 or any Pass amps on the B&W. 
I have heard Pass amps on different speakers such as Focal, Magico etc But not on B&W. 

I I agree with Georgehifi. Your noisy fan on your Classe CA-2300 was probably caused by dirty filters on the fan. You might want to check your filter. Cause the fans on all my Classe CAM-600, CAM-300 & two CA-2300 amps that I have in my dedicated HT room are silent and barely barely audible. My dedicated HT room is very well treated and get dead quiet when there’s nothing being played, and while it’s true that I have a very large dedicated HT room.

Which Classe Omega amp is it that you saw for sale? Was it the Omega stereo amp, Omega monoblock amps or the Omega Omnicron monoblock amps, which are lower end series of the regular Omega monoblock amps.
The Omega stereo amps are even older than the Omega monoblocks or the Omega Omnicron monoblocks.
I believed that the Omega stereo amps were first introduced in the late 90’s, whereas the Omega monoblock amps and the Omega Omnicron monoblock amps came out in early 2000s if my memory served me well maybe between 2001 to 2004 I think and remained in production until late 2000s around 2008 or 2009 or maybe even 2010.
Make sure you get the one from late production around 2008 or 2009. You can ask the seller for its serial # of the amp and once you have it, I would suggest you contact Classe give them the serial # of that Omega amp and ask them what year it was being manufactured.

@73max

You might want to clean the fan filter.

In regards to the Classe Omega Reference monoblock amps that are for sale and were purchased new in 2004. There’s no way to confirm that unless you get the serial # from the seller and contact Classe and give them the serial # and ask them what year the amps were manufactured. The Classe Omega amps are still the best sounding amps that Classe made and are superior sonically to any Classe Delta series amps.
These Omega series amps are pure class A deigns whereas the Delta series amps such as your CA-2300 are class AB designs. Those Omega series gears were very expensive more expensive than the Delta series gears.m
The Omega Reference monoblock amps original retail price was around $30k or $35k for the pair when they were still in productions.
Sometime certain Classe dealers still are able to get V stocks of these Omega series amps brand new directly from Classe.
My local Classe dealer here had a pair of these new Omega Reference monoblock amps v stock brand new form Classe 2 yrs ago.

+1 @georgehifi
Your Classe CA-2300 amp is a perfect choice for your B&W 802 D3. If you want to upgrade, you can get the Classe CAM-300 monoblock amps or the CAM-600 monoblock amps. Just clean the fan filter.

In most ideal scenario, autoformers won't be perfect choice for your B&W 802 D3. Classe amps will be better choices for your B&W 802 D3.
I've heard the B&W 802 D3 driven by Mac MC601 monoblock amps and have compared them with the Classe CAM-300 & CAM-600 monoblock amps in the same setup, and the B&W 802 D3 sounded best driven by the Classe monoblock amps. I've also heard the B&W 802 D3 driven by your Classe CA-2300 stereo amp and it was even better than they were driven by the Mac MC601 monoblock amps. 

The Classe Omega Reference monoblock amps are phenomenal and indeed superior to all Classe Delta series amps including the CAM-600 monoblocks, which is the flagship in the Delta series amplifier line.
If you still want to purchase those Omega monoblock amps from 2004 I can only say go ahead but you will need to send them back to Classe in Canada to get them looked at, to see if the caps or anything that need replaced or serviced.