Sapphire 7790 ATI video wont pass the bootup with Ubuntu 13.10 (but it will with an older card).

I am setting up from scratch, with an Asrock 970 Extreme r2 motherboard, FX 8320 CPU, WD Green 2TB Sata HD, and 8GB Kingston HyperX RAM. I believe I have an issue with the video card: Sapphire HD 7790 ATI 2gb
First time, I ended up sending back the motherboard, as it had an issue. Finally starting with the replacement, and while I can at least load up Ubuntu (13.10), after setup and restarting (all fine to that point), it gives me notice that it has to go into low-graphics mode. There are options to troubleshoot and restore, but they are dead ends. After clicking on them, the same popup window shows up. The only working option is to agree to enter low-graphics mode.
And then, after a few black screens and some white text (command line startup stuff that is beyond me), it freezes.
I tried going through the setup procedure a few times, and several reboots, to no avail.
*ONCE, it got through to the regular desktop, but while it was in "low-graphics" mode. It then asked to download updates (I agreed). After that, it needed to restart. After the restart, I was back to square one: Selecting the low-graphics mode during bootup, and subsequent freezing.
I took out the video card and tossed in my 8yr old sapphire whatever card: Boots up to desktop!

So I suspect the video card isn't playing ball, but don't know if I need to return the card or if there's a workaround I'm unaware of. I would test out the video card in another computer, but I don't have access to another motherboard that will physically accept this card.
I have looked at a few forums, but don't see anyone with this exact problem.
I'd appreciate hints, help, or direction.
Thanks