DS-X: Absolute shit, and should be burned. A user named p1ngpong is trolling. If you don't know what that means, then it means they're pretending to like a certain product, item, or anything on the internet, but they actually don't in real life.
R4: It was good in the times, now it's just outdated, and not worth buying. Too expensive for what you get.
Acekard 2: Best budget card. Unless you're getting the DSTT for it's price. I think it's worth the few bucks more.
Acekard R.P.G: Great card. It's probably the fastest improving card out there. Unfortunately, it's around 80 bucks.
N5: 50/50 chance of killing your DS's fuse. If your fuse is broken, your ds is pretty much dead. There are ways to fix it though. NOT WORTH IT.
Cyclo: Best of the best, in the current times anyway. Great features, great team, etc. Kinda expensive.
SCDS1 SDHC: Does everything the Cyclo does, but more. More features, a team that never drops support for any of their products, and only 31 dollars. Unfortunately, it's not as fast as the Cyclo, and has a more complicated GUI. Might be hard for newcomers to use.