I did exactly the same upgrade with same issues. Also added a movable 10" JBL wedge cabinet behind the second row (it also fits behind 3rd row if they are up) w/ JBL 300W Class D amp for bottom end. I tried double 10's for a while but found it to be too much. I am missing some frequencies due to road rumble so originally thought I needed a 12" but am thinking now that two 8" subs might be better. Anyway - sounds like you like the Infinities - I think they are a bit bright but really smooth.