madafca what exactly are u looking to get as far as hardware.... im guessing a workstation this way evrything is all in one unit, but i have no idea what sort of sounds or features your intersted in.
a 800$ budget is good, u could get 2 or 3 peices of high quality pro gear if u shop around.
i would say your best bet is a korg triton le, it does evrything on it and the sounds, synth engine (HI system), effects and sampler are GREAT. the only thing is the sampler is not built in, you have to get an add on. and the keyboard action sucks, but thats only if your used to high quality keys, but if this is your lil brothers first synth he wont know the diffrence. the triton le 61 keys used sells for around 600$-800$.
also a roland xp-50 would be real ill and you would have like 400 or 500$ left over for something else.