I've already chimed in about the Spark Mini amp. Just wanted to say how much FUN this old guy is having tonight with it.
Just kicking back tonight, cool evening breeze flowing through the house, got my Spark Mini, headphones on and jamming along with some of the blues tracks within the app. Whats really cool is how you can speed up or slow down the tracks provided. That is of a huge help. All I can further say is I wish I would have bought this little amp much sooner than I did.
In my very humble opinion, for my needs this is the best tool for learning and improving on guitar. It's opened doors for me.