Really, two pro cams and two consumer cams.
NX70 - if you need a compact and weatherproof pro camera
AC130 - a well-rounded handheld camera for a pro
X920 - high resolution and good sensitivity, but must be crappy usability from my previous encounters with the SD600, TM700 and TM900, though granted I haven't used the X920 and I've heard it has slightly different (hopefully, improved) menu system. Really, it cannot get any worse than the TM900, but hey this is Panasonic, they can screw all the good stuff they had. Allows full manual exposure control though.
PJ790 - don't care for modern Sonys as they don't have full manual exposure control. Otherwise should be a solid consumer cam.
P.S. Image quality is everyone top priority, this is silly to even mention as a criterion. But maybe you have something else in mind, like size, portability, certain features, must look professional, must have dreamy movie-like DOF. Maybe you want certain codec, although all these come with AVCHD. Do you want to shoot presumably handheld, or from a tripod? Do you need XLR connectors? Lots of questions.
My take is that you don't know what you want or need. In this case buy a used cam off eBay for $200 or so, start using it, then you will figure out what it lacks and you will buy your second camera fully knowing what you want.
I was interested for the NX70 because I like small feature-packed cams, but then I've heard about issues with its stabilizer or was it something else, so I crossed it out.
I never wanted the AC130, I rather wanted the HMC150 for 3CCD. Anyway, both are too large for an amateur and have only 1/3-inch. These are journalist's cams.
The X920 is one of the best consumer cams, hopefully Panasonic improved the horrendous menu known from earlier models.
As I said above, I don't care for the consumer Sonys because they lack fully manual exposure control.
P.S. Get a used HMC40 off eBay for $1200 or so. Lots of features, great image quality, light sensitivity is not stellar, kind of two generations behind current consumer Panasonic cams.
Edited by Ungermann - 7/10/13 at 2:52pm