G729a on VIA Processor Eden 400

Hi

could anyone advice what type of G729a should i purchase.

running asterisk 1.2.9.1 on VIA Processor Eden 400 MHZ with 1GB RAM

codec_g729a_v32_c3-2 or codec_g729a_v32_c3 or something else

and what is the maximum number of channels VIA can handle ?

thank you