Class A vs AB

IIRC Nelson Pass himself has stated the "transition" is seamless, and has expressed dismay at audiophiles who seem to expect some kind of "kathunk" on the cross into class AB territory. 

The high bias isn’t just so that the first X Watts are "pure class A" - it’s so that the class AB watts sound better. 

IMO you’re much much better off this way than with a lower power pure class A amp that will be running hard and risk clipping during peak demands. 84dB sensitivity at 4 ohms generally means 81dB per Watt (84dB being at TWO watts). That’s extremely low efficiency.

I've run high bias AB SS amps at higher volumes, and never experienced any discernible transition or the like to give me pause.

Here is the balance the way I see it.  "Current" is what pushes the woofers, and this is what makes bass.  For super efficient speakers, the highs and mids are loud without much current which can hinder the movement of the woofer cones, thus giving you less bass.  A good integrated tower speaker will address this topic well.  So, overall, what are you getting with the much less sensitive Arandal vs the Fritz?  If it is bass you are looking for, then, you may really get it with this switch.  The trade-off maybe the top end smoothness and dynamics of the Class A at high volumes.  Tough decision, but, it sounds like you are a rock & roll fan, so, bass is key to sonic bliss.  If this is your need, then, I say "go for it".  Note:  you will still get your Class A at lower volumes. 

You will never know what you are missing if you don't try.  Just do it.

You mention the level you play at but that's an average. If your music is dynamic with large momentary swings you need power to not clip them. And peaks can be 10, 20, even 30 dB and you will be out of class a.

By the way, almost no push/pull(non single ended amp) is really pure class A. It's very rich class A switching to class B. For instance Nelson Pass's class A amps have a class A power rating but they typically have 2 to 3 times that power where they switch to class B momentarily so the peaks are clean. 

I wouldn't worry about staying class A. Stay with your amps and they are probably class A over 95% of the time.

This link might provide some context.

I would be mostly concerned that my amp would sufficiently deliver the power so that I could easily listen at the levels I want.  As @hjdca said, you could give it a try.  There is nothing wrong with the sound of a good Class AB amp and your amp was meant to cross seamlessly into AB as needed.