Thanks for the reply!
Im pretty sure the sub swap is possible using a line out converter (such as the one made by PAC etc.) I looked at the thunderform & stealthbox but found them a little pricey. I cant change stock nav head unit because it displays the hybrid powertrain info on my truck, so you can understand why I dont want to sink too much into this. I think the setup above will sound nice, it wont flex body panels...but that's not what I wanted anyway. Clear, strong, bass at bearable sound volume levels is what im after.
i got the upgraded thunder form packs plenty of punch..