firstly, sack keys off mate, you're gonna get something insanely shitty for that price.
secondly, buy second hand, if you're gonna spend fuck all it'll most likely keep the resale value.
thirdly, save more cash, seen arturia microbrutes going for about 160-180 second hand, well well worth that little bit extra.
if you wanna ignore that then here's some stuff
korg volca keys or bass.
second mutable instruments shruthi-1 - sounds awesome, digital synth with analogue filters - i want one badly!
waldorf rocket, also want one badly!
dave smith mopho desktop - absolutely bitch to programme and probs not worth your time