I don't have experience with Blaupunk but I did get a cheap $35 Belva amp off ebay after my car got broken into and I just needed to get a amplifier that was cheap to hold me over for a few weeks till I could afford to get a new pair pioneer amplifiers and I've used boss audios cheap 4 channel amp and planet audio 2 channel 1000 watt and Crunch 4 channel Amp 1000 watts and they all where less than $60 and worked very well. Aside from the boss amplifer only lasting 7 months for the price they get the job done and better than you'd think. I even had the crunch 4 channel 1000 watt amp powering my four cabin speakers off 2 channels bridged and a Apline E12 bridged off the other 2 channels with a low pass crossover switch to LPF. The biggest thing I look for if going for a cheap amp is the fuse on the amp and what its rated then test my charging system while the car is on and have everything turned on and the hvac on high to see what it's voltage out put is at that point of high use simulation. As long as it it's above 12.3VDC you can keep going. If it's below 12.3 or at 12.3 VDC then you need to fix your charging system somehere. But multiply whatever your multiplier showed your power was times the rating on the fuse and that'll give you a rough idea if your car how many watts it'll push out and then you can avoid getting a cheap amp that clipps and burns your woofers oiut.