actually you should make a new topic for it.
but you need an mk4-mini with a neo2
about downloading roms try google, or p2p or something, we won't give links and they will be deleted if said by anyone.
but the neo2 has three version:
1. the lite version, has build in memory space op to 1Gbit(128 MByte) so it can play the largest roms for now, but maybe not in the future, maybe bigger cards will be released. I don't know. It has changeable fronts so it can fit perfect in the nds-lite, and with the other front it fits perfect in the normal ds.
2. the SD version: uses sd-cards(not yet mmc cards but they will be supported in the future). it is as big as a normal gba-card so it will stick out on the nds-lite but fits perfecty in the old fhat DS(only the sd-card will stick out but RS-MMC cards will not stick out but they aren't supported at the time). with an adapter you can also use mini-sd and tf cards on it, but you have to buy the adapter yourself.
3. the TF version: uses tf(micro-sd) cards. is very small so it fits perfect in the ds-lite(only a tiny stick out where the tf-card enters) bot DOESN'T fit in the old fhat DS.
my choice would go to the SD-version because it is cheaper than the neo2-lite if you buy an sd-cart as big as the biggest neo2-lite. also it fits in all DS's without changing anything so if you're friends want to play but they have an other ds they can just plug it in.
and although the SD and the TF version cost the same(according to
www.ic2005.com)SD cards are still cheaper than TF cards. and you can't use the TF version on a old DS.