Differences between Parasound A23 and A21?

I understand the basics from their website, but it does not say if the A21 uses any higher quality parts other then the case work and possibly in the larger power supply. I emailed Parasound a while back and did not get a clear answer other than "it is closer to the JC1's then the A23." It appears from their specs that it is just an A23 with double the power, but I have not been able to verify this either way. If anyone has a clear answer I would appreciate your experience. Or if you have had a chance to compare the two amps with the same speakers I would also appreciate any feedback you may have.
If you don't need the extra power there is not a huge difference. The A21 does have a much larger power supply. If your speakers are bi-ampable and reasonably efficient you could use two A23's to bi-amp keeping one stereo amplifier for each channel. Since you already have an A23 this may be the easiest and cheapest upgrade.

Good luck!
A21 is definately better. I've listened to them both extensively. The A23 is good, but the A21 is quite a bit better. Clean, low level detail, improoved bass control, higher damping factor, ect. Higher class A bias. It's worth the upgrade.
I too feel the A21 is a nice step up from the A23. Just put them side by side and look at them. The sound is analogous to the physical differences.