The AS-3000 is their high end product, as such it is probably specified much more conservatively. If you look at Marantz and Denon's equivalents (pricewise), they are also specified at around 100W, or less.
I have no doubt the A-S3000 may actually be more powerful than the AX-1090 for low impedance loads under certain conditions, but the AX-1090 will be more powerful than the A-S801. In real world applications, the AX-1090 could be as, or more powerful than the A-S3000, despite it's lower quality power supply.
For $300, if the AX-1090 is in good operating condition, it is a better buy unless you need the additional features that the 801 (I assume there could be 1 or 2) may offer.