6 GB of RAM is not enough for any game in Win7.
Though, I've found out that even 8 are not enough, if you are disabling your pagefile and have 40 Chrome tabs running underneath.
With 16BG though, I haven't got yet any system memory low warning.. yet
Hyperthreading is an Intel technology which add a virtual core on each processor's real core. The result is tat it is doubling the cores, but that's not too ok for unoptimized multicore applications. Clustering a real and a virtual core running on same core, and leaving other real cores unloaded will lead to performance loss. Usuallu, the operating system is the one which should do all this job, and split the requests amongst the real cores first, but it never worked fine in intensive applications. And there are no applications, or very few, which are managing their load on different cores by themselves.