Class 2 is fine. The Class refers only to the write speed, not the read speed. I use a 16 GB Class 2 card on my Tilt2, and it plays music and video just fine. I upgraded from a 6GB Class 4, and have not noticed any difference in read speed. Writing large files to the card will be slower on a Class 2 versus higher classes, but not a big issue for most people. I can see how the class may possibly be an issue for phone that record HD video (where a high write speed may be neccessary). But for the Aria, the higher Class card are probably not worth the $$$ (and have been hard to find lately).