You really cant get one that is too big, but you can buy them without features they should really have. You get what you pay for basically.

I use and recommend the APC RS Series.

http://www.apc.com/products/family/index.cfm?id=349

If you look at the page, the main difference between them is how long it can run the computer once the power goes out.

I use this one on my workstation

http://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=BR1200G-JP&total_watts=200

It will run it about half an hour at idle, then it will shut the computer down with the software that comes with it. It hooks to the computer with a USB cable to tell it to shut down.

They have plenty of outlets (5 surge/backup, 5 surge only) on them. The batteries usually last about 4 years and are easy to get replacements and replace.

The BR1200G retails for about $250.00, and can save you thousands on the first brownout or spike.

Just keep in mind that any one of these can still fry everything after it if the spike exceeds the maximum it can absorb. I have had it happen, and it is depressing. Some manufactures will offer protection insurance, so fill the card out and mail it in, register it online, etc.

Excellent post! Basically exactly this. The more "power" a UPS has, the longer it will run your devices on battery. So no, you can't buy one that's "too big" other than it might be too big for your wallet. :P