Not at all, I use 2x250 SE's on a 36" parallel/parabolic reflector for my 65.
In hindsight, I would go with a T5 6-7 bulb setup driven by an ATI or Icecap ballast. You'd get more light output (IME) with about 100 less watts, bulb replacement costs would also be also be about the same when compared to replacing 2 MH bulbs.