Dual Channel?
Well after everything I've read about Nforce2, the concensus seems to be that there is hardly any benefit in running dual channel on that chipset. At least not enough benefit to outweigh the cost of adding the extra memory and added stress to the memory controller. In short, you do gain a small edge on performance, but u can lose out on some fsb. This is my interpretation on dual channel and nforce 2.
In terms of what memory you should get, again the concensus seems to be "get bh5". The Buffalo 3700 has bh4, so do Hyper X 3000 and 3200(non-A). Corsair use to have bh5, but not anymore. Im not sure about A-Data though. To answer your question about what memory spec to go for. You will not need to get PC4000, seeing as how the timings are completely ***. Since most ppl don't "usually" go super high fsb(230+), you can still get away with PC 3200. But just to be safe, get the Buffalo 3700 with BH5. You should be able to get tight timings with those chips. If you can't get Buffalo, then get HyperX or anything else with BH5.
EDIT:
OMG I totally forgot about Muskin Lvl 2 Black Pc3500. Its the only one rated for 2-2-2 timings at that spec. Then again tho, Buffalo is still cheaper.