Best P5ql Pro Qvl Choice

Hi

I have a Kingston 2Ghz DDR 2, 800 mhz kit on P5QL PRO and i want to install 4 Ghz RAM.

What is the best Kingston DDR 2, 800 mhz from the QVL a can choose to P5QL PRO + E8400 ?

Is it better to have 2 x Kingston 2Ghz DDR 2, 800 mhz kit (CL 5) or its better a 4Ghz DDR 2, 800 mhz kit (CL 6)? According to QVL?

Thanks for any help