You could replace them with high end subs and it will sound a little better but with them only being 6 1/2 inches you will not get any "big" bass from them. There's no way to install larger subs in a coupe, I looked at this option. I'm not sure about in a roadster. Remember that this is a 2 ohm system so the bass blockers from crutchfield etc will have a high cut off as they are made for 4 and 8 ohm systems. I don't think the money it will cost for good 6" subs would be worth it.