my .02
I put a "plus zero" on my RX330 and actually noticed that there
really wasn't a whole lot of difference...
That being said.. If you just go wider... let's say 20 mm (which is a bit over 3/4 of an inch)
that also increases the sidewall (which I agree with a previous poster) which gives you
more cushion..
A co-worker has a 2005 LX M/T and has 17" rims on it (a daily driver) and he thinks it rides
to rough.. I *think* he has 225/40/17 which (to me) are like bicycle tires... :-)

 

Make sure you are running the proper pressure in your tires. The sidewall number is the MAX pressure you should never exceed. This is NOT usually the pressure you should be running your tires at. Chalk across the treads and roll the cara few meters to check for even wear. Wear on the edges means not enough air. Wear on the middle means too much air.

Run adjustable shocks/struts or put back in the soft stock springs andinstead improve your handling by way of stiff anti-swaybars and sturdy strut-tower braces. If the ride is still harsh, pick a rim/tire setup that has more sidewall to it.

 

hum.... never heard the chalk idea.......

 

Ditch the 17's