Imo, avoid Sony in-car stuff at all costs. Its absolute cack. I used to work for Sony, me and all my colleagues could get Sony in-car at trade price and we STILL didn't want it lol.
A quick fyi on car amps in general, most (if not all, i havent had time to check every sinle one lol) has stereo mode AND bridged mono mode. You can see from the first amp you posted that it actually runs at 250W peak when used in bridged mono @ 4ohms. So not quite as bad as originally thought, but still nowhere near enough.
My suggestion would be to pick up a copy of a magazine like this:
http://www.motorpoint.com.au/australianinc...nt_magazine.aspAs pimpshiznid said, Rockford Fosgate make very good amps and subs, also check out Alpine, JBL, Infinity