Another good option is a DSONE SDHC card if it's for DS/DS Lite only. They have more features.As for me, I would recommend an Ace3DS+ clone: you will easily find it on Amazon, eBay and Aliexpress as a 208in1 (or 408in1) cartridge. Very cheap, it uses Wood kernel (so very compatible and working with demanding titles like Ni No Kuni eng patched) already included inside a micro SD along with various roms that you can eventually delete and replace. Also very good is the r4 gold pro, perhaps the most advertised in Europe, but you will have to use YSMenu instead of its own kernel.
Your choice.