AFAIK Crucial and Corsair seem to have the best reputation for memory pretty much, but Corsair seems more expensive.
I need to get 2x 512mb DDR PC2100 that are stable - I'm not bothered about o/c. I'm pretty certain that anything above PC2100 will be wasted by my setup (see below), therefore would I just be best going for 2 Crucial 512mb PC2100, rather than 2x Corsair PC2700 (or TWINX PC2700). It seems that Corsair don't do PC2100, only PC2700, is this correct?
Corsair is worth every penny. It is (and has been for quite some time) arguably the best memory you could buy. They hand-select their chips for performance and reliability. You will not regret going to them. Read through the threads here as well as the articles on Tom's, and I'm sure this will be echoed over and over again. Check out their site at <A HREF="http://www.corsairmicro.com/" target="_new">corsairmicro.com</A> for further research. Check on <A HREF="http://www.pricewatch.com/" target="_new">pricewatch</A> fur the most current prices.