Parasound A23 or HCA2200ii for Sonics Allegra

Looking to buy a used amp in the $500-600 range to drive a pair of Allegras. I was originally thinking about the A23 but am starting to think the HCA will be a better value, allowing me to later upgrade the amp by installing improved components as the money/desire comes along.

Any suggestions?
Well I decided to go a slightly different route and try out a McCormack 0.5 Deluxe...
Can't imagine you will regret it, the 0.5 is a sweet amp with a well-defined upgrade path and fantastic support through SMc Audio. If you ever have any problems, give Steve or Kris a call or post here; Steve regularly responds to posts about his products.
I'm definitely excited to give this amp a try. Don't have anything now to compare it too, but I can't imagine after reading all of the reviews that it won't be more than adequate to get me started. I'm sure I will begin to test multiple amps against it when the time comes...