I own the Bel Canto evo-4 and, in my opinion it is an excellent amplifier. Driving ribbon speakers like Magnepan, it was the best amplifier that I used. It excels driving B & W's too. Zero grain, even response, very extended, transparent and powerful.
I believe the IRD is a conventional amplifier (class AB). I am sure it's very good too but, after going through several conventional amps, I doubt it will be too much different than the others - some traits they tend to share. One area they may have an edge is in depth. The soundstage depth seemed better with the better conventional amps. The transparency and immediacy seemed much better with the BC.
Having said this, there are many amplifiers on the market today and, generalizing is probably not a good practice anymore. As in speakers or any other component for that matter, preferences will play a large part. If possible, try before you buy. Look for the companies that offer money back trials. I don't like returning an item any more than someone else but, in this hobby there isn't a way around it if we are intent on assembling that magical and often elusive system. Several circle vendors offer a money back trial (NuForce, IRD (I think), Channel Islands, etc).