Hello.
Another vote for the SUA1500 here.
I did my research in 2008 just after buying my MP1.1. It seems that waking up a MP1.1 from sleep will overload just about anything other than an SUA1400 or SUA1500 including most of the Back-UPS series.
So I settled upon a used SUA1500 vintage 2004. It's been flawless, though the original batteries died last month.
My advice is to stick with the SUA series. The construction and particularly the cooling is better. Sine Wave output is friendlier to the expensive Power Supplies in your Mac Pro, Monitor and anything else plugged in.
Have you ever disassembled and inspected a UPS? I have. The Cyber Power 825? 850? I looked at is a piece of junk. Over-rated, tiny 12v battery, relatively thin, badly routed wiring, no cooling fan, hardly any slots for cooling air, that thing looks to be a bigger Fire Hazard than anything else.
In comparison, the SUA1500 has very heavy construction, 24v battery pack (twice voltage=1/2 amperage) and very good fan-assisted cooling.
Even being generous and calling that CyberPower 825 a "750VA" for being supposedly half a 1500VA rating, the battery is a tiny 9AH, 1/4 the size of the SUA1500s total of 36AH.
You may think: Well, it'll just run a shorter length of time before the battery runs out. Yes, but with much higher internal temperatures cause by shoddy, undersized components and wiring combined with poor cooling, the risk of unstable power, possible damage and even fire is just silly to take.
You bought a Mac Pro. This is one of the best (and power-hungry) Desktop computers ever made. Don't get all cheap on the UPS.
Better to just plug it into the wall than into a time bomb.
Have Fun,
Keri
PS.... Looking for some evidence of shoddy construction? This one is WAY better built than that Cyber Power thing I looked at:
http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=159
PPS. There's all kinds of unsafe junk out there that burns down houses without making the news. Bestec Power Supplies found in eMachines and HP computers set many motherboards, keyboards and mice alight when their 5v standby power goes to 12, 16, maybe 20 or 30v... I haven't heard of any recall.... Any what about Diablotech, POWMAX and ULTRA PSUs? A lot of those went boom with sparks and flame too..... Where's the recalls?