Old Grey Haired Man wants some boom!

[MashTheGas 72]

I am almost 50 but I still like my tunes, and yes BOOM. I wanted to know the best and less expensive way to go. I will need an Amp, stereo, and subs, speakers.

1st would it be best to just cut out my dash to accommodate a new unit.
2nd has anyone been able to mount subs behind the seat with gas tank still in.
3rd where is the best place to mount my amp, Under seat?
4th I was looking on amazon and found a woofer setup that looked like it would go under the seat.
5th Has anyone installed a stereo with full DVD screen.

Pictures would be awesome of your setup. Thanks a lot for your advice in advance.