If you are still looking for a modest hotel in Aix, I can highly recommend the Hotel Cardinal. It is one of the nicest 2* hotels I've ever been in: large room, very charming pretty decor (flowered wallpaper and bedspread, etc), and a huge tiled real bathroom (and that was a single). It's very convenient also as only a block or so from the art museum and a couple blocks to the main drag (Cours Mirabeau). I actually walked to it from the train station with my rolling suitcase, also (it's about 6-8 blocks perhaps) although I took a cab back for convenience.

Here's a list of 2* Aix hotels. I think the Cardinal and the nearby Hotel Quatre Dauphins are the best bets in this category:

http://www.provenceweb.fr/e/bouches/.../hotels2st.htm