Ahh. Didn't notice that you were in Australia and those were Australian dollars, my bad. Actually I was talking about the AMD Athlon 64 4000+ which is $334USD I believe. But the 3700+ is only one step below and is equal to a 3.7GHz Pentium 4 (thus the "3700+") in regular tasks like you mentioned. However in games, the 3700+ is MUCH better, more like a 4.2Ghz Pentium 4 or something like that.
DDR is as strong as ever and people will be building systems with it for a long time. However AMD's Socket M2 is coming out. Its basically the same processor, except it supports DDR2 memory. Still nothing wrong with DDR right now.