I own the 1820m with EmulatorX and have successfully paired it with an MSI Nforce2 mobo. Both are working in blissful harmony although I'm notorious for really pushing my cpu's performance by loading a lot of fx and synths. Either way, I've learned to live with the limitations of my system.
As for your nforce4 mobo, you will find a lot of success stories at www.emuforum.info where I am also a regular member. There is a member there named Guitar23 who uses an MSI A8N (sic) Neo 4 Platinum and he has no probs at all.
With most forums, you will always find the occasional disgruntled ex-user who has never cracked open the manual to make his Emu work properly. This is not a soundblaster that you can pop into any open pci slot and have it work flawlessly. It's true there are other cards out there that work fine out of the box, but they don't have the Emu's converters.