If you don't upgrade your stock 6.5's (front and rear) with two decent component sets and a good 4 channel amp, you'll never hear vocals with two decently powered subs of any size. Speaking from experience, I'd good with a high-end dual voice coil 10" or 12" in a sealed box with about 500 watts at least to compliment two 5.25" component sets with a 200+ watt amp. BTW, I enjoy death metal as well. :twisted: