It definitely doesn't sound like a 5 watt SS amp :) IIRC, the Celestion Blue is pretty efficient, so the 7.5 watt setting still makes some noise (i.e. you can use it with a drummer.) BTW, I've plugged the output of my old Champ into the 2 12" speakers in my Twin, and that's got some volume too. It's not just the wattage rating that determines your volume.
If you can, try before you buy. I think you'll like it. I did a side by side with the AC15CC1 and there is no comparison. They're completely different amps IMO.