The performers I have seen have a varied mix of transport and it's funny that it's almost totally relative to the amount of income they have available to invest. I saw Eliot Lewis a few months back and he used an iPad. Of course he does pretty well as a member of Daryl Hall's band as well as having AWB on his resume. On the local level I have seen more generic types of devices, but they all do the same job, so "whatever you have" seems like a workable answer. I have gone round and round about the "quality" of playback devices, but whichever you choose, it boils down to some executable program is playing back some data file, and it doesn't know if you are at The Carnegie Lounge or Carnegie Hall. Myself I would go iPad, but that's just because I already have it. If I didn't, I'd go laptop, since I have 2 of them. And if you went laptop, you are just playing back wav files so you don't need a rocket sauce super computer. If you picked up a used laptop and loaded some music player (I like VLC - everybody has a favorite) it would be fine. I would make sure it has an SD slot so you can use memory cards that you can move from studio computer to laptop as you move files. Again, some use USB devices, but I like as few "moving parts" as possible, An external hard drive can fall, a thumb drive can get snapped off, etc.....

Plus Steve, you know a good computer guy to help you make a used one run like new....