What didn't you like about them?
I'm still looking at ways to add the SoungSurrounds to my family room system. The family room is awfully tight and I may be stuck continuing with a dipolar surround. If the FR doesn't work out then I'll use the SS in the bedroom. But they are 4ohm speakers so I'd still have to buy a receiver and a center so we're back at spending about the same amount of money. But yes I've been keeping this idea in the back of my mind.
Honestly I listen to the bedroom setup maybe an hour a day and 90% of that is movies/TV and 10% listening to music while I fold laundry. On the other hand I practically live in the family room so it made sense (well to me anyway) to spend well in excess of $4k not counting my sub for that room. That's where I do all of my critical listening.
The main difference will be that any of the Song series speakers will be much more clear across the midrange. Once you get used to that, there is no going back to other speakers without it.
The Usher S-520 would be a decent speaker except that it lacks baffle step compensation. It overemphasizes the midrange. There is a peak in the response around 1 kHz, followed by a dip. The overall effect emphasizes voices and brass, but in a way that actually smears the sound. You lose clarity and detail instead of emphasizing it. If you keep these speakers close to the wall behind them, this problem is much less apparent.
I don't remember the M22 very well, except that it doesn’t come close to being in the same class as the Song series speakers. It didn't sound very clear and it started sounding like it could become fatiguing. I only listened to them for a few minutes.
I can't remember if you got the SongSurround I or SS II. The SS I is 8 ohms and is no problem for any receiver that I know of. The SS II is a 4 ohm speaker, but just like the ST, is not a problem for any receiver capable of delivering an honest 50 wpc at 8 ohms. When I first got my STs, I used an older Denon 70 wpc receiver without any problem. Try your receiver and see if the protection circuits kick in. If not, then you are good to go. I wouldn't automatically assume you need a new receiver to drive them.