I suggest not getting any type of R4 whatsoever unless you are dying to have WoodR4, then get the R4DS, but as stated above, it only works on the Phat/Lite DS'.
If you have an AK2i, just wait for AKAIO 1.8.0 to come out. It's rumored to be near a release, though don't quote me on that.
And as...