Mortifix you may want to look into the EZ4. the ez3 is almost impossible to find now and cost way more than the ez4 with a mini sd. i jus ordered my ez4 from www.gamersection.ca . they are located in canada and shipping isn't too bad. u can buy a cheap 2gb card from newegg.com or frys.com. the 2gb cards will only cost u about $20 with shipping and u should be able to fit 200 or more gba games on there.
i'm unsure of cheats (however check the file fast6191 linked u to, it has a guide and all the programs needed), but if ur looking something thats just gba and is cheap thats the way to go. the ez4 can also be used for ds games assuming u have a passkey of some type that works for it. i believe chism released an AR thing a while back, that u might be able to boot on ur ez4 and insert ur ds game into the first slot to run AR codes on ur ds game.
the only problem is that this might be just a little bit out of ur price range, but its one of the best around, and probably the cheapest way of doing this and having good compatability.
http://www.gamersection.ca/product_info.ph...products_id=147
or
http://www.gameyeeeah.com/ezflash-ez-flash...sd-c-24_51.html
(i've never had experience with gameyeeeah but they are an affiliate of gbatemp so i'm sure they would be fine)
as for memory cards, since u live in the USA i'd reccomend buying from newegg whom i have ordered from several times and have had no problems.
http://www.newegg.com/Product/ProductList....916&name=MiniSD
u dont need to worry about memory card speeds because the ez4 has built in flash memory on which it loads the gba rom from the miniSD card onto, which simulates an actual gba cart (no slowdowns in games)
u can read up on the ez4 here -
http://gbatemp.net/index.php?showtopic=32250
http://www.iso420.org/nds/ezflashiv/index.htm
another alternative u might want to check out is the g6 lite. i'd advise you to stay away from the supercard. it's going to cost u about the same price if not more and has worst gba support. the ds side of things might be a little bit better, but i absolutely hate my supercard rumble i bought a while back from them