if new my suggestion may well be t-amp such as the Topping TP-20MKII
and I'm going to admit this is going to put you over budget.. but
and then save monies for sub later.
so you are using your brothers stereo now? is there any part(s) of it you can run for now??? or is that not an option?
finding something like you are looking for used even at $150 is tough... but I have living proof not impossible
I just this week got a fully functional Denon AVR-688 for $25
but that is kinda crazy good pricing..
and I have multiple sets of speakers that I love that would probably be great for this
using these with my yamaha RX-573 in the living room Paid $20 B&W V202 speaker..
and I have these FANTASTIC... JBL L1 bookshelf speakers paid $40 for these.
These Bang & Olufsen RL 60.2 speakers I grabbed for $60 awhile ago.
so as you can see around here anyways USED..is freaking awesome... requires patience and luck however sometimes.