UPS Backup Recommendation

APC is the best way to go and yes as stated above you can use their wizard to work out what is best, but I would recommend probable a SmartUPS 3000 or similar size, which should give you a reasonable amount of time to turn everything off, as well as capable of taking a little more should you buy extra kit, you can also get the network management card for the IP Web Based interface and external temp sensor.

Okay I think I am decided on APC, I think the SmartUPS might be a little bit of an overkill... I was looking for something under the thousand dollar range.

APC is def the right one to go for,if you do not have the budget for the SmartUPS look at the BackUPS, but I am worried a BackUPS may be too small for the power you need and the battery time of 10mins.

My recommendation – be sure that you will have correct UPS sizing.  For example UPS Smart SC1500 have Output Power Capacity 865W! (1500 are VoltAmpers). 10 minutes of runtime when 700W loaded.
If you have new servers with PFC power supplies check bottom link from APC about right UPS selection. I have experience that people works with “Marketing” value and use VoltAmpers for UPS sizing.
http://www.apcmedia.com/salestools/RMUZ-7DTKRC_R1_EN.pdf
regards
btb

APC is by far the leader in UPS technology plus they are legendary. So you are on the right path!
 
You have to keep in mind that servers handle electricity much more precisely than desktops/laptops do. For example new DELLs can’t run on anything other than pure sine waves (Smart-UPS). You are also saving the life of the server components by insuring there is less fluctuation in wave forms and voltage (safeguarding against step-approximated (pseudo) sine waves and other electrical anomalies).
 
I don't know the specs for all your servers but i would definitely *not* recommend a Back-UPS unit for servers under any circumstance for a number of significant reasons: (the list literally goes on & on)

1. Topology - Back-UPS *do not* produce pure sine waves, which servers’ require. Back-UPS aka an "offline" UPS - it means that it’s not doing anything much until there’s a powercut - when the main fails, a relay closes, the rectifier based battery charger reverses to become a basic square wave inverter that creates a pseudo-sine wave output running from battery power to supply your machine. Smart-UPS use "line-interactive" technology - it still means there is a relay in the circuit, so you still get a small break in power supply, but a Smart-UPS also incorporates a transformer that gives additional filtering for mains interference such as spikes & RFI, and it also can give boost/reduce by automatically tapping or removing another coil on the transformer to reduce the impact of brownouts or surges. They produce a pure sine wave output.
2. Transfer Rate - Back-UPS *do not* have a fast enough transfer rate (8-10 ms), whereas Smart-UPS are 2-4 ms. In many cases 8-10ms is so long that the power will fail to backup due to this lapse.
3. Voltage Regulation - Back-UPS *do not* have AVR (automatic voltage regulation) – it auto corrects low & high voltage conditions & manages them accordingly without using the battery.
4. Power Conditioning - Back-UPS *do not* have Power conditioning – it protects connected loads from surges, spikes, lightning, & other electrical anomalies (sags, brownouts, etc.)
5. Hot-Swappable Batteries - Back-UPS *do not* have clean, uninterrupted power to protected equipment while batteries are being replaced.
6. Scalability - Back-UPS *do not* the ability to expand batteries by adding additional batteries to provide longer time off-line.
7. Proper Shutdown Procedures - Back-UPS *do not* the ability to shut down servers properly nor their apps e.g.( MS-Exchange, MS-IIS, MS-SQL Server,Lotus Notes/Domino, Siebel). By design they put a desktop in hibernate mode, which servers do not operate in by default.
8. Network Manageability - Back-UPS *do not* have remote management of the UPS over the network.
9. Notification/Alert System - Back-UPS *do not* have alert capabilities via phone number or emails sent during critical events such as critical temperature changes, power failures, battery replacements, etc.
10. Predictive Failure Notification - Back-UPS *do not* have provide early-warning fault analysis ensuring proactive component replacement.
11. Automatic Self-Tests - Back-UPS *do not* the ability to run periodic battery self-tests, which ensures early detection of a battery that needing replacement.
12. Equipment Protection Policy - Back-UPS *do not* as high a policy payout (APC Back-UPS: Lifetime: $75,000) vs. APC Smart-UPS: Lifetime: $150,000).
13. Equipment Protection Policy Validity - Back-UPS *were not* intended for servers so you may jeopardize your policy payout entirely. Just as you would if you connected them to medical equipment, etc.

IMO I would rather sell one of the servers, consolidate apps & buy a SMART-UPS than run 4 server with no UPS protection or a Back-UPS. Each environment is different and certainly if you have bad electrical it will dimish the life of all your equipment but typically once you buy a SMART-UPS it will last 2-4 yrs before you need to buy another battery. It’s well worth the investment to justify the expense.
 
Smart-UPS is by far is the only choice of the two. Use APS’ online configurator that RGRodgers mentioned to locate the desired specs, runtime & features: http://www.apc.com/tools/ups_selector/index.cfm.

Sorry for all the typos...i left out a lot of "have's". :)

APC might have twice the market share that Eaton has but you shouldn't dismiss them from the equation, in fact you'll probably get something equally as good for less because of it.

http://powerquality.eaton.com/UPS/selector/SolutionOverview.asp

meshoxford,
Have you reached a decision yet or are you still waiting on more info?