Given the M3 with the rumble/ram pack is cheaper and is virtually the same as the CycloDS, and that you can get the M3 with the GBA pack for roughly the same price... I think the M3 is the better choice. You can run iSaukra/etc to do virtually anything, or stick to the official USA firmware and have working realtime saves.
I actually already have a M3 unit for the GBA stuff. I have the good one that had onboard ram. It is setup to play GBA games as I see fit. I may get the CycloDS but if you have a particular M3 that you want to recommend then let me know.