I dont think Little Dot I and FiiO E9 are classified as portable amp... I would recommend Lisa3 and sr71 to drive your hd650, but both of them are over your budget. If you wanna fully drive your hd650, use a home amp

I would prefer paying a bit more and get the latest model, SE215. The price for SE215 is just USD$90 in amazon US ,including two years warranty and the headphone is actually brand NEW! I had the 210 and I can say the new design for SHURE IEM is a lot better; more comfortable and with better...