are you really set on PQI? i just checked their site, and ugh... if you really want to OC i recommend newegg as well.
as far as what PQI has to offer tho, i could only find 2 kits of dual channel memory for 2gb. model # PQI24200-2GDB and #PQI3200-2048DB both have a lower latency than model # PQI25400-2GDB. but reviews from all show that quite a few of the boards were having problems recognizing either set properly. but none of these perform as well as the below items:
if you want a little more problem free, try some OCZ
from Newegg. more expensive, but more reliable. (minus a little manual settings, mobo rarely recognizes the true speed)
but....if you really must have PQI, go with model #PQI3200-2048DB