Mute sims are a lot of expert only charts featuring difficulties ranging from 9-14, most hovering the 10-11 range. They have multiple difficulties and transition into hard stuff, and the songs are enjoyable by most. The official In The Groove packs are very good. Here's a quick explanation of all of these packs - mind you they are all on our local machine in Houston TX, so they are definitely doable. Trancemania 2 (Even though it is listed as Keyboard, it is meant for pad) The packs I am about to list can be found on this website.
(That means they won't have 'jump stream' and the patterns were designed to be followed on foot. Mind you, I'm a pad player, and all of the songs I will be linking to you will have multiple difficulties ranging from beginner to god damn Mad Matt.