Just make sure you stay away from the HCCA 250 G5 and the HCCA 275 G5. Both of those amplifiers had a higher than 50% failure rate back in the day and some were known to catch on fire.
On the flip side, if you get a first generation HCCA 250 or HCCA 100, make sure you get the bridging module with it. You can build your own bridging module, but it isn't for the faint of heart if you aren't into electronics!
The Digital Reference through the HCCA G5 don't require a bridging module.
Now for some useless information: I bench tested my HCCA 225 G5 and it produced 73 watts per channel RMS @ 4 ohms just prior to clipping on my oscilloscope. My HCCA 250 G5 produced 100 watts RMS per channel @ 4 ohms just prior to clipping. In other words, even at 4 ohms they are grossly underrated:veryhapp: