I am in the same boat. I've had an xbox1 modded for a long time now and just got a NDS lite. I was looking at the various options for homebrew, music etc..., and from what I gather the DS-Xtreme, looks to be the best cart out there, and the M3 simply, and R4, are the other top options.
With the DS-Xtreme I don't like the fact that you are limited on size, and if you want the bigger size (which you do because Nintendo just upped the size limit on games) you have to pay twice as much as the M3 Simply or R4.
With the M3 and R4 I am worried about wifi play (I've heard Mario Kart doesn't play well w/ wifi). I am not to concerned about the Download Play feature, but I definitely want wifi play.
Today the CycloDS Evolution
was announced and it looks to be promising.
So basically I'm looking for input from everybody. Has anyone had problems with wifi play on any cart, what cart would you recommend, etc.?