Right, Monkey stop talking about stuff you don't really know. His RAM is running at 166 MHz, because that's the speed of his FSB. I.e. you can't change it (without overclocking blah blah). However, being DDR (Double Data Rate), it's actually running at 333MHz (DDR333), which is PC2700. So basically, there's no point getting ram that is better than PC2700 (Unless you're running an Athlon64 setup?). It won't run any faster. Having said that, PC3200 is often just as cheap as PC2700 anyway, so you might as well just get that (PC3200 is backwards compatible down to PC2700). You might as well just get the cheap stuff, save a few quid. I don't think you need the "premier" stuff really. OCZ is a pretty reputable make, so any will definitely work. And the more expensive of the two you posted just has a heatspreader, which does bugger all. So I wouldn't get that. Just don't get ebuyer super value ram :-
EDIT: And yeah, you should be able to run them both together with no problems.