As for a descent computer for my normal tasks, I would probably be fine with a Dell Dimension 8400 configured for $1500. A comparable G5 would cost at least $500 more.
" if I can find a descent KVM"
I think the mini uses USB keyboard and mouse.
I picked up an older model (ADB, the mid-80s to late-90s Mac keyboard/mouse connection standard) KVM box, for an arcane purpose, on (I think) eBay. Used. Works fine. The arcane purpose is to try hooking an optical mouse to an Apple IIgs, which actually was the first Apple model to use ADB.
OTOH, for the cash you may be better off just getting reasonably priced USB keyboards and mice. I see your point though -- just switch the kb/m as needed.