Thoughts on amp brands

Hey,
i just bought a zero watt head unit
kenwood excelon x915
i allready have a mono amp for my sub
now i need to pick up a nice 4 channel amp for my speakers
i want to go with at least 50wX4
but i don't want to blow alot of cash
i've been scoping amps on ebay looking for a good deal
i could kick myself because i missed the closing of an auction for a kenwood 848 that went for $80
here are the amps i've been mainly looking at

kenwood
pioneer
alpine
profile (california)
rockford fosgate

just wondering if anyone has opinions about what companies make good amps and which ones to stay away from
if there is an amp i left out tell me why you like it
also keep in mind that i intend on spending around 100 on this amp and that i have no real problem buying a used one

thanks guys

Sean