I'm looking for a new UPS to replace an almost 10 years old APC beast that's having issues, but I'm not sure what to buy.

I'll be using it to power a small home server and some network equipment in an area where there are occasional power outages (but they last 2-3 hours). My requirements are:

• 300-600€ range
• At least 1500VA, 900W
• Doesn't make noise unless it's on battery
• Must not require proprietary software to monitor it or to calibrate the battery and other basic stuff (if it works with apcupsd or NUT it would be perfect)
• No weird battery format

What would you recommend?

Thanks!