well like jolancer was saying the lower is better but, with fast memory with low timmings you will need a bit more voltage running to it than regular high timming memory, your average pc3200/ddr400mhz memory with timmings 222-5 would use about 2.7-2.85v. but the memory i am running is geil ultra ddr500/pc4000. timmings 2.5-337/ 2.9-3.2volt, so most likley the higher mhz the memory will be timmed higher. but some memory modules like voltage for example say some memory is 3448 timmings pc3200 2.6-2.7volt you could proubly run 3.2volt to it and crank it to 2336 timmings pc3200, ive seen my memory run at 2336 @256mhz effective 512mhz! with 3.5volt to it, and these results were dont on a p4 3.6 with the ocz dimm booster, so make sure you can always run a little more voltage to you memory.
