typical over-rated budget amps, but if you like the price I'm sure they'd work ok if you don't abuse them. Keep in mind you won't get near rated power out of them. Especially the 880. It's rated for 150x4 at 4 ohms -- no way. With 2x25A fuses there's no way it's going to produce much more than 500w, 600 tops. So that would indicate 150x4 at TWO ohm stereo (300x2 bridged), and probably more like 100x4 at 4 ohms stereo. All things considered, a good amount of power for a <$150 amp. The big question is - will it last?
The blx4000 is a low impedance amp. I can't help but wonder if a cheap amp like that can withstand that level of stress.
I'm no expert, but I have a Boss Ripper 565 1000w peak that I've had for 4 years. It's a little rusty in places but it works just as good now as it did when i bought it. PtP