What memory specs should I be shooting for?

I'm putting together a new computer with some donated parts, but I'm pretty clueless when it comes to getting memory that will play well with the rest of my system.

I have an Intel E6600 Core Duo (2.4 GHZ, 4M L2, 1066 MHz FSB), which I intend to overclock to ~ 3.0 GHz (I've never overclocked before, so I'm not going to be too aggressive with it).

My motherboard is a Gigabyte GA-EP45-DS4P (P45, 1600/1333 MHz FSB)

I was given 4 sticks of Crucial Ballistix 1 GB DDR2-800 (2.0V, 4-4-4-12) memory, but was told that one or more might be bad. Rather than futz around trying to figure out which ones work, I figured I'd upgrade to two 2GB sticks.

The two options that I'm currently considering are:
1) G.Skill 2x2GB DDR-800 (1.8-1.9V, 4-4-4-12)
2) G.Skill 2x2GB DDR-1100 (1.8-1.9V, 5-5-5-15)
They're both similarly priced, but I'm uncertain which would give me the better performance - faster speed or better timings (or whether something entirely different would - I'm not wedded to the brand either, so long as it's reputable).

Thanks in advance!