96HOE

ok so im debating on getting a stinger 50 farad cap to go along with my sk-bt120 shuriken batt or do you think i should just get another batt to help keep higher voltage in my 96 tahoe??? current equipment is as fallows and alts are in the making 2-2100rms brz amps strapped / but only able to run one of them currently due to voltage dropping super low 1- sk-bt 120 shuriken 2600 amp batt big 3 done stock alt at this time all tsunami 1/0 guage wiring 2- fully loaded Fi BTL 18s 20 cubic ft box tuned at 21hz any suggestions??? could use the help A.S.A.P. please