I need to choose an amp to replace my JL HD amp.(600/4) It's between Zapco DC100.4 and MB Quart QAA4250. I will be running Hertz Mille up front and MB Quart QSD in the rear. My sub is a W7. Zapco is used and MB Quart is new. about 75.00 difference in price. HELP!!! Thanks in advance!!