APC batteries are jelly bean parts. You can probably go to Batteries+ or whatever and get some new ones without it being a huge deal honestly. The lead acid stuff is somewhat "safer" than the Lithium Ion shit that'll burn everything down if it charges wrong. Look around online too, some of them have hereditary problems batteries won't fix. Varies from model to model.
So, a few things on KVMs since I have one successful and one not successful install at the moment:
-If your monitors take HDMI or DVI input you're good to go. You just get the adapter cables and go.
-Displayport, HDMI and DVI outputs from a computer are fine going through an HDMI KVM.
This is where problems start. My work has issued me a set of Displayport only Dell Monitors. They DO NOT work with HDMI or DVI adapter cables using a DVI Source to drive them. I have tried a few different adapters and both an HDMI and a DVI KVM. For me to make use of this setup, I'm going to have to change monitors. The other options are that I get a DisplayPort video card or that I get a USB keyboard/mouse switch and return this then run monitors separately.
My wife running HDMI/DVI monitors works perfectly though. Her thin client is displayport while her docked laptop is DVI through an HDMI KVM. The one I got seems nice enough, for an extra $15 or so you can get a nice remote button too.
At that point, yeah, I'd look for an older 'cheapo' server GPU from Nvidia or AMD. Something that Dell/HP/etc would throw in a server to get video output but not much else since all you'll likely need is dual 2D 1080p. Can probably find a refurb for $100 or less. I wouldn't go with any of those USB based piles of shit.