politik: I'd recommend a 1GB kit.. for that would ensure you can easily hit the 4GB mark on popular boards out today incase you ever need that much RAM. Speaking of boards, they're pretty expensive in general at the moment too. Infact, many people are actually using Conroe and it's effects on the price-wars to get a super-cheap AMD X2+ for dirt (aswell as a generally cheaper 939/AM2 mobo).
Templar: I would actually say the 4MB cache can be rather advantageous, if you're not someone who upgrades often. According to AnandTech's benchmarks, some productivity benchmarks showed a ~150-200MHz-equivalent advantage of having a 4MB Core2 over the 2MB version. E.g their OCed 2.6GHz E6300 performed roughly the same as their stock E6600 and their 2.88GHz E6400 ~ stock E6700.. and this was almost certainly evident in alot of their gaming benchmarks too (such as Quake IV and F.E.A.R). 150-200MHz is alot of power for a Conroe. Secondly, the benefits may become amplified since I intend to run the E6000 @ 3.5GHz - 4GHz (i.e by the time I'll be taking proper advantage of a 4GHz Conroe, I'd probably need such a high amount of cache to give my CPU a more balanced performance output). That is, the main thing is really just for futureproofness. The extra cache might not bring me a huge increase in performance right now, but then again I don't exactly need a 2.4GHz E6600 for practically anything I need to do night now anyway. I won't be spending money for a new PC again after Conroe for another 2-3 years and there's a good chance that the higher code data sets which will inevitably arise from future games and productivity software will start to take a much bigger advantage from the extra 2MB.
Edit: I'm waiting to hook a nice E6600 up with a R600/G80.. or even 2x 7950GX2s if they come down to $500AUD by Christmas and that nVidia actually releases some good drivers for them soon.