Photoshop isn't a bandwidth limited application. Encoding audio or video is bandwidth intensive. Not all Dual channel DDR logics are the same or greater than each other. Intel's Granite bay and SiS' 655 are just about the only true dual Channel DDR logics for the consumer. SiS 655 having greater performance at a cheaper price is what most Pentium4 users are aiming/currently using. The performance gain from Granite bay migrating from a Dual DRDRAM chipset is dismal. You might as well stick with the current chipset you have unless you plan on buying the SiS 655 chipset, which is the best performing Pentium4 chipset that features Dual Channel DDR and a small price to pay.
If you're thinking of Dual channel Nforce, then forget it. The second channel isn't the benefit for the Nforce2. It's the advance prefetching and tailored drivers Nvidia implemented. The second channel is only meant to feed the IGP when it is in use. If you're using an External graphics card, then the second channel is just spilling bandwidth to a 'blackhole'.
The programs that work best is diVx encoding or Windows media encoder, Mp3,OGG,or Ape/monkey audio are bandwidth intensive. File compression such as Rar and other types of compressive work can benefit from it as well. Although it isn't exactly earth shattering, it gains.(very little if that).
NLE setups have there benefit as well. But i wouldn't have high hopes for performance increases from that as you can pretty much do that type of work on any chipset that supports DDR.
But then again, i have been known to be wrong.
