Around what price out of curiosity?If you are looking to play DS games on a 3DS or DS and want inexpensive look for a genuine r4i 3ds, or spend a little more on Supercard DSTwo. You should be able to get a mainboard with a lower firmware for a decent price if you shop around.
Also Chris230291 Supercard DSTwo costs about twice as much as an r4i 3DS, but it benefits in many ways (GBA/SNES emulation built in to name a few).