PCE Everdrive sounds like the way to go. I was always a little weary of buying a NeoFlash 128. This is why I have been holding out on getting one, even though I came close to getting one almost.
I didn't get one mostly for these 3 reasons:
1) Build quality. Sometimes they won't work with your system or in Sign of Zeta's case, not at all. blehhh
2) 128mb internal ram. It is enough memory to enjoy quite a few games, but seems a bit annoying to have to delete games to put more on.
3) No extra features similar to a Pro Action Replay for example. This of course isn't huge deal, but would be very nice.