Using outboard sounds also lightens the CPU load of your computer.
Yes, I have found that the softsynths are great but they really tax the system. I think a really good deal is the Kurzweil K2000 or K2vx - you might find them for $400 too. It seems to be a higher quality instrument in all ways. I compared midi on a roland to the kurz, and the kurz had more levels of distinction. The roland seemed to be more extreme with less expression in playing notes on the keyboard and capturing to midi. The kurz also has good drums, pianos, strings, etc. (I have the K2vx with the orchestra blocks too). You could actually do almost an entire traditional band on it and there are a number of analog synth patches too.
In fact, I have discovered this paradox. I had some drums played in Midi on the kurz that sounded good. So I sampled the hits, and put them in Battery to have more control and sample accuracy. However, they just don't sound as lively. Strange as it sounds, the drums sound better being played with Midi from the Kurzweil.