I bought my M22 v2 speakers back in 2008 and I've had absolutely no complaints for the last 6 years. The speakers still sound amazing. I've told myself that I would eventually add additional speakers and sub for a 5.1 system and it the day is finally drawing near. My question is whether I'll notice a difference in sound or tone of the speakers if I purchase a new center, surrounds and sub that are v4, while continuing to use my M22 v2 speakers as the mains?

If there will be a difference in sound, is it even going to be noticeable outside of a direct A/B comparison?

I use M3 for surround at the moment with M22 for mains, a few months ago Got a Vp160 Absolutely love it.
The only big difference i've noticed is in power supply.
I went from a budget amp. Onkyo 525.
Wanted to get away from Onkyo and purchased a Tascam PA-R200.
Witch turns out to be a rebadged Onkyo Integra 30.4 But it's fantastic so much more headroom Toroidal transformers makes a tone of difference in sound quality.

Without knowing anything about your room or system....

I'd buy towers and a center and bump the M22s to surround duty. You'll be good to go. Just make sure whatever you do the front soundstage matches. (But I bet the differences between V2 and V4 will pale in comparison to other variables affecting sound in your space.)

The 525 is definitely a wanting AVR on paper. Congrats on the upgrade!

I'm interested to see what others say here. I grabbed a set of M22 on walls before xmas from the refurb shop. They are V3's, but look quite a bit different from other V3's I have. Logo is older, black dust caps etc. They must be very early V3's. Of all the b stock,refurb speakers I've gotten from Axiom these are also the most....um...worn looking. I really should have sent them back.

Anyways, I kept them, and decided to get the rest for a 5.1 setup. Grabbed some M2 on walls, and a vp 150 all V4 speakers. Could not be happier with them. But, now I don't like those M22's even more. Even the M2V4's sound better. Its weird. They sound harsh when pushed.

There was a set of M22 on walls in the refurb section again two days ago. Light Maple, exactly what I was waiting for to match a set in another room. Added them to cart and hesitated. I let the cart expire and added them again several times throughout the day, each time hesitating. Eventually someone else got them. I was worried that I'd be unhappy with them again.

So, there you go. Is there a difference? My experience is yes or I got a bum set of m22's