I just bought an N5 Revolution.
Bad move, the N5 is a cheap R4 clone that's been known to actually break DS systems (how, I have no friggin clue).
The couple places I went to in pacific mall (most of you probably haven't heard of it... it's like an all out chinese mall) said that the R4 is discontinued.
Dunno about that one, though it's a bit harder to find nowadays.
The R4 isn't necessarily bad, it's just outdated with all the newer carts on the market (SDHC support being the main feature the R4 lacks). For a new user, I'd recommend looking into the CycloDS Evolution, Supercard DS, and Acekard (either v2 or R.P.G.). The SCDS has the most features, with the CycloDS Evo coming in at a very close second. For homebrew, they're all about the same, though the SCDS has more stable soft-reset patching for homebrew programs than the current CycloDS Evolution beta firmware.