I'd echo what rrlev says regarding v4. If your m22's are 12 years old than id go for the upgrade to v4. I have ti series and v4 series and the v4 series are better. They have a "wider sweet spot" and the mid bass has more texture and definition and is just plain better, highs are better tempered, softer (in a good way) and very enjoyable, they do the disappearing act really well and easily too.
I think mojo brings up a good question as well, what power plant you are using? My M60ti went from good to amazing when I added in seperates with well endowed clean power, it really made a huge boost in performance and enjoyment. I tried the big power amp on the m3v4 too (carefully of course) and man did that sound really good in my bedroom setup. REALLY good. Tons of seperation and very strong imaging with depth, it's probably my favorite setup of them all.
Do you use the left and right channels for pure 2 channel listening too? That's also a consideration whether to upgrade to v4 m5hp or even v4 m22, v4 m22 might integrate better with your ep500 over the m5hp....not totally sure on that, i'm a rookie at sub woofer integration but learning with my 2 subs and my m60ti.
