There are quite a few nForce 2 chipset combinations. The newest two are the nForce 2 Ultra 400 (dual channel memory) and nForce 2 400 (single channel memory). Both of these support a 400 MHz FSB, which the 3200+ uses. The version of the nForce 2 with the integrated GeForce 4 MX will not support a 400 MHz FSB, only DDR 400 memory, according to nVidia. This means that any nForce 2 based board with integrated graphics will never officially support the 3200+, only up to the 3000+. (This is not the same as DDR400 support. All nForce 2 chipsets can support DDR400 memory, but only when the integrated graphics core is not enabled.)
There are also two different southbridge options for the nForce 2 chipset (MCP and MCP-T). One, the MCP-T, has the desirable Soundstorm audio and a lot of other nice features. This is the difference between the Asus A7N8X and A7N8X Deluxe.
All nForce 2 boards perform best when the ram is run syncronously with the processor's FSB, meaning that running the ram at 333 MHz yields top performance on the 2500+ - 3000+. Only the 3200+ requires DDR400 for top performance. Using DDR400 memory AND running it at 400 MHz actually hurts performance on the 2500+ - 3000+. (You could go into the bios and force the ram to run at 333 MHz if you used DDR400. Only if you planned on overclocking a 333 MHz FSB Athlon XP or using a 3200+ should you be using DDR400.) So, yes, a 2500+ will perform best when using DDR333.