I know I forgot about this thread for a while, but I also didn't use the Mac Pro directly much for a while. (It does a lot of file serving to other devices)
Someone mentioned "4K boot screen". Just to clarify, I don't actually need the boot screen in any particular resolution. I just need some kind of boot screen. I have every hard drive bay filled... and my boot drive is partitioned. Holding option shows way too many drives (but most of them aren't boot drives, makes it more frustrating).
Furthermore, the graphical glitches are getting worse on the 5770. They get worse the longer I use the computer (card is heating up?)
Some years ago I used the card to do a lot of bitcoin mining, back when you could actually do such a thing and earn an amount of money greater than zero. This entailed a lot of time booted into Windows XP, with the GPU overclocked a bit. I think the card is now paying me back for that torture: 4K is stressing it enough to cause these transient glitches.
I'm not doing video editing work or anything like that. I just like "the big iron" and the fact that with the right upgrade I know I can run this Mac Pro for another 5 years at least. The only thing that really took down my G5 was removal of PowerPC support from software (and the fact that my old MacBook Air was faster), and I expect the only thing that will take down my Mac Pro will be something similarly significant.
So I'm still confused as to which card to get, but I have to get one soon, it looks like.
The 4K monitor is huge and there's basically no room on my desk for a second monitor. I have a nice 20" Cinema Display going unused right now.
The start up procedure sucks so hard though, I'm afraid to reboot the computer now or shut it down or anything. I have to have a better startup procedure.