If you are not very experienced in discrete designs, or may not have the time or equipment, I would suggest using Hybrid Amps like STK or LM.
There is nothing wrong with them. Think of them like instant noodles. Its edible, fast to cook and gets the job done with the minimum fuss.
As for a sub woofer amp, you are not very concern about the high frequency performance. What you would want is an amp that can produce good bass, loud enough without distorting. In other words, a properly rated transformer and enough capacitors and depending on how loud and how long you play, how big is your heat sink.
An elderly STK084G can deliver 65W(RMS) into 8 ohms and 110W(RMS) into 4 ohms. According to the specs, the newer STK's like the 4048XI can deliver 150W(RMS) into 8 ohms. These hybrids have come a long way. If you need more power, bridge them.