Adequate dual-core performance at an affordable price? That'll be the Pentium D 820.
It may be produced using relatively ancient 90nm manufacturing technology and based on Intel's soon-to-be-extinct Netburst architecture which lacks many fancy features, such as shared cache memory and boosted SSE results, of the new Core 2 range. But for most applications, most of the time, it does the job.
Indeed, our only real concern is dodgy gaming performance when running at the stock 2.8GHz clockspeed. For almost everything else, including high definition video decoding, it puts in an extremely plausible performance. And even the mediocre gaming frame rates can be remedied by cranking the clock well beyond 3GHz. If this is all you can afford, you won't be overly disappointed.