Is it a 15 or 20 amp circuit. If it's a 15 amp circuit you have 1800 watts available which we would only put 1440 watts on (80% for continuous load).
For rating purposes a receptacle is usually rated at 180W.
2*60=120 (new lights)
total 1920 watts
If it's a 15 amp circuit you are already overloaded on it.
I hope it's a 20 amp circuit which would be 2400w. The total for a 20 amp circuit would be acceptable but maxed out for design purposes.