Definitely without - the butterflyes get in the way when your benching and they only hold a pathetic amounf of weight anyway.
I think you'd be better getting squat stands and an adjustable bench - it will cost more but you will have a far greater choice of what you can do - those york benches don't have very high maxes for the load they can handle.
Have a look here:
http://www.fitnesspeak.co.uk/acatalog/HeavyStuff.html