Don't get an R4. Get an Acekard 2.1. I would recommend the CycloDS Evolution as my first choice, but you're looking for cheap flashcarts. The CycloDS is 50$ but it is the best flashcart out there. I won't go into details.
The Acekard 2.1 is the second best flashcart, and if you are looking for a cheap one, or can't pay the price for the Cyclo, then get the Acekard 2.1.