Just to get this straight -- they reccomended new shocks and springs because of the weight of the bike, or for another reason?

New and better shocks such as those made by Rancho or Bilstein will aid your ride and handling (on and off road) tremendously regardless of carrying your bike or not. The stock ones just don't really hold up all that well.

If the load capacity is what you're after, instead of changing out your springs you may want to add a Firestone air bag system. I've helped put two of these on friend's trucks (one who carrys his dirt bike on his 4runner, the other a cab-over camper shell) and they work great. Not that hard to put on and a breeze to adjust.

You don't mention if you're going off roading or want a lift. In that case, the air bags won't help because they link the axle to the frame and will limit travel.

Hope this helps somewhat. Welcome to the board.