Nak Headunit With Updraded Components And Amps?

[92Lex]

has anyone ever kept their nakamichi headunit and install upgraded speakers, sub, and amp? i have a 92 ls400 and i was wondering if its possible...i like the stock headunit look but just want better sound and more bass. any suggestions for good 4" components? also, whats the biggest sub that i can get into the sub enclosure on the rear deck without any real modifications? any suggestions on which sub to go with? any help would be greatly appreciated. thanks.