I think the UPS you have Vulcan is a 500VA one, not quite the same as 500W (
http://www.dansdata.com/gz028.htm)
If you are getting frequent brown/blackouts, a whole house surge protector will help but won't be everything.
http://www.hgtvpro.com/hpro/np_produ...484609,00.html
Maybe whole house surge suppression combined with a UPS on expensive stuff like home theater and computer?
I've got a 1500VA UPS for my office and a 500VA one in my basement for my router, modem, and NAS.