I have been perfectly happy with APC powerstack 450 - use it with Behringer X32 Rack + Apple Airport Extreme - got it used and have had it for two years now - spent months in truck in winter - no problems at all. Only thing I do not like about it is it´s weight - it is heavier than X32R + rack combined.
We've been using the 700VA on small items for the last 18 months or so, and they've been fine for simple UPS units. Nothing to write home about, but no hiccups either. FWIW, we also keep a SurgeX in front of them to take any potential hits, so the Cyberpower boxes are strictly doing UPS duty (DSP, small digital consoles, etc).
I use that exact one in 2 of my racks. Never had a problem with them. They are a bit weighty, though. But you would expect that. They sit in the bottom of both racks giving them more stability.