I'm pretty confident that encoding items and the flight simulator do not support dual-core CPU's, that is, unless you were talking about doing both simultaneously, in which, a dual-core processor would surely pull ahead. As already stated, dual-core is only useful when you are doing multiple things at one time that require a lot of "juice", or using an application or game that supports dual-core processors (basically, none, hopefully more items will support it soon though). So if you are constrained money wise, a single core will suffice. However, Intel has already dropped single core CPU's altogether in there newest line of CPU's, after the Pentium series is dropped (rather soon I'd imagine, before 2008 probably), all their CPU's will be dual and quad core. So in all honesty, a dual-core CPU is probably the way to go, as it's actually hard to find a solid single core CPU that is not overly priced (FX series for example ... )