Wow i build it ! ...... But need some tests! Today i find some bugs in it and i'll fix it later, and later i'll post pics and specifications. This PSU WILL NOT SUPPORT stand by mode, because i read many threads about dryed batteries. Then i made PSU which in off-state don't takes any current- NO any MICROAMPS - i think it's great. I think hibernate - is very good choice, and it's work fine.
What about controller ?
Here is a simplest controller - 5 seconds before startup , and 15 seconds before shutdown, it monitors voltage of battery, and have a rem output to control amp or lcd - it takes hi state after 0.5 sec of carputer on , and low state before carputer shutdown. When it shutdowning, it waits 40 sec , if windows isn't shutdown- controller shutdown all system hardly.
This psu fully isolated - no more buzzing or interferrence

No need ground loop isolator.
You can( to avoid ground loops - must) powers from it usb devices and lcd monitor.
Ok today i tested it on this hardware at home
proc. Celeron D 2133MHz (overclocked about 3200)
mb. asus p4s800
video geforce 2 mx400
mem. don't know manufacturer - 256M
HD. WD 80gb
cd- samsung 52x
dvd liteon combo drive
modem conexant56 soft internal
so it's work great
hmmm........
i think i'll really finish this project