I've been wearing two Siemens Signia CICs for the past 6 years and it's probably time for an upgrade.

However, the local representatives here in Athens, Greece where I live don't seem to know much regarding technical specifications (they mostly talk about the number of channels) and I'd like to do some OBJECTIVE comparisons before starting to try on some new aids.

What technical specs should I use to compare hearing aids -- compression? matrix? output/gain? And what do they all mean?