What makes it faster? Lower latency or higher bus speed?

I need some help.

I am building a system with an Asus P4PE mobo (845PE Chipset, 533MHz
FSB), to be upgraded to a P4C800 (875P Chipset, 800 MHz FSB,
Dual-Channel DDR400 Memory). Both have flexible CPU Core Voltage
Adjustments in 0.025V increments over defaults, adjustable FSB/DDR
ratio, fixed AGP/PCI freqencies, frequency selection at 1MHz
increments (from 100MHz up to 200MHz on the P4PE and up to 400MHz on
the P4C800).

I will be starting with a 2.4GHz 533FSB and eventually upgrade to a
3.0GHz 800FSB.

My objective is to overclock to the highest operating/user experienced
speed I can.

I am totally new to overclocking so I do not know exactly how lower
latency compensates for higher bus speeds when it comes to the final
user experienced speed. Thats where I need some help.

Right now I am shopping for a couple of 512MB RAM modules (for a 1GB
board). I came down to a few options from Corsair XMS line:
1. CMX512-2700LL: 333MHz 512MB (64Mx64) and CAS Latency of 2-2-2-5-T1
2. CMX512-3200LL: 400MHz 512MB (64Mx64) and CAS Latency of 2-3-2-6-T1
3. CMX512-3500C2: 434MHz 512MB (64Mx64) and CAS Latency of 2-3-3-7-T1
4. CMX512-4000: 500MHz 512MB (64Mx64) and CAS Latency of 3-4-4-8
5. Other?

Having in mind that I plan to upgrade to the P4C800, which of the
above is likely to let me best overclock? Why?

I really appreciate any help.

Thanks,
Daniel