Wow 2x for 600? I wouldn't even think about it twice. XS's in my area in running good condition go for 1,100+. I bought mine which needed: re-wiring, rotor, fork rebuild, tail light, rear suspension, gas tank, fuel lines, petcocks, almost new carbs, exhaust, new engine covers, new sprockets, new chain... the list goes on and i paid 900 (way over paid it was the only one available at the time so i said screw it i waned to get my hands dirty!)
If the other has a right side engine cover with sight glass and you want to part it out i would love to make an offer for it!
Maybe that and some other covers / misc parts.