There's a chart with reviews here: http://www.nds-gear.com/choose-which-ds-dsi-3ds-card (I've heard that 3DS system updates may block flashcards). I plan to get an Acekard 2i myself; I have an R4 SDHC but the firmware update process for that card is a bit convoluted.
Yep, I can vouch for that...
As long as you update your flash cart BEFORE you update your 3DS firmware, you should be fine...
...but err on the side of caution anyways, the internet can tell you whether or not it will work...
Bookmarks