Hyperthreading is an Intel technlogy which basically simulates dual core processing on single dual chips. It does increase performance, but it will not provide the same results as literal dual core setup.
For your requirements, I would recommend a Celeron or Sempron. Yes, many people will tell you they are the lower end of the technology availible today, however unless you are doing larger, number crunching processes, you do not require an Athlon or Pentium.
The Celeron/Sempron route is the better choice for you in my opinion, you don't really need the larger cache size, and the L2 cache on some of these processors are starting to increase so they are not as bad as they are made out to be. Even better, they are much more cost effective processors.
Intel C2D E6320 / AMD Athlon X2 3800+
Gigabyte 965P DS3 / DFI nF4 Ultra-D
2GB OCZ Gold PC2-6400 / 2GB OCZ Gold PC4000
eVGA 8800GTS 320MB / eVGA 6800GS 256MB
150GB Raptor / 74GB Raptor
2x500GB / 320GB
OCZ GameXStreme 850w / OCZ StealthXStream 600w