Nothing with external storage will have perfect speed and compatibility.
I recommend the X-ROM 512 from easybuy2000.com. Check reviews of it.
dude.... they haven't had X-Roms in stock for years.
not to mention the battery is not rechargeable, dies all the time, and replacing it is a **** pain in the ****. not only that
but the EZ3 is more compatible with games.