Kernel version and zaptel

Can anyone recommend the ‘best’ kernel and zaptel versions to use with asterisk?

we’re currently running trixbox and are having numerous call quality issues
(disconnects, echo, garbled speech) and I’m considering wiping the asterisk box and installing a virgin copy of centos, compiling asterisk myself and installing freepbx on it’s own…

Is there anyone who can recommend specific software versions that have been proven to be stable and reliable?

We’re running trixbox 1.2.3 in case anyone has similar issues that they might know how to solve