The a300 sensor (same a200 sensor) is a new version of the K10D/GX-10, D80, D40x and a100. This sensor is a new SuperHAD with max ISO 3200.
Here is the example to ISO 800 between a200 (same sensor) and K10D:
http://www.imaging-resource.com/PRODS/K ... LI0800.HTM
And here to ISO 1600 NR off
The noise control is good in the Alpha cameras and the a200/a300 is entry level segment and the K10D is like D80.
The noise, for me, is better in a200/a300...