Esper22

There is a good youtuber thats from your neck of the woods that has a pc enthusiast/hardware/budget chanel might want to check a few videos out. Might be able to get some used hardware and then upgrade from there that could strech your budget into a really decent machine. Ill look up the chanels name.

Keeping the 2 rigs completely separate from each other will help with the chances/minimize the quantity of possible noise or interference the two systems could create and in turn have to deal with. 2200va for big rig,  1500va for the smaller one, 2 different circuits.

I would say unless the 1600w or grater psu calls for a 30 amp standard nema 30-5r receptacle then that the 2200VA ups should be enough. Idea being that you have already oversized your psu for no more then 80-85% capacity used so the 2200VA ups should be more then enough for complete protection.  

I'd say unless your going to use a 20 amp spec cord from the outlet to the power supply like a nema 20-5p (the one with a sideways power prong a normal outlet or a spec grade would be just fine. The 1600i probably comes with a heavy whip with it but idk refer to the manafacture included items.

Ok so as far as electrical wiring goes 1600W @ 120V 60hz usa power your looking at 13.33 amp potentially for just the Desktop. Safe continuous power draw on a 15 amp circuit would be 12 amps by industries standards. If you go this route discribed i would run a 20Amp dedicated circuit for your setup (12/2 romex ) on a separate 20Amp breaker.  A new 20amp circuit would allow  16amp continuous draw  ( 1920 watt max).  Been earing a living as an electrican for 18yr now.