Tires: wider tires, size rims, r15 tires

Question
I'd like better handling in my Volvo S60(non turbo)2.4 and currently have 195/65/R15 tires. I'm actually curious why larger tires/rims weren't factory installed to begin with....but will getting larger rims and tires (16 rims) help much or harder edge tires, etc help?

Answer
Ken,

Upsizing - going larger in rim diameter, while maintaining the overall diameter - directionally is towards abetter handling vehicle.  However there are some things that tag along:

Upsizing also results in worse ride, fuel economy, wear, and hydroplaning, but better dry traction and wet traction (except hydroplaning).  But careful selection of tires can change any of these properties.

Doing this is somewhat complex, so I suggest you consult with a retailer such as Tire Rack, or Discount Tire.  They've done this type of thing many times and have a good system to select properly size rims and properly sized tires.