Your getting an opus 90w so no you don't need a tank circuit or a ITPS. Better order that OPUS 90W right now. I could probably sell mine for 300%
Don't forget about the GPS receiver and program. Some will say its not necessary but I say it is. Why else are you making the carputer?
And is that a laptop hard drive? Just some personal experience I had 40 gigs before and it was not enough, now even at 60 gigs it runs out quickly.
Don't forget the various wires, adapters and usb hub/firewire.