On the advice of several folks on this forum, I've decided I'm going to buy my (very low mileage) 2011 AWD IS350 when the lease terminates in a month. I'm now thinking I would like to do something to improve the handling a little bit, and I'm now looking for some insight regarding the F Sport suspension upgrades.

1) My options seem to be a rear sway bar, which I have read is a significant improvement. I might also consider the springs.
2) Although lowering the car is not my primary interest, I understand that the springs lower the car about an inch, which will reduce the wheel gap to about what it is for a RWD IS, which is about all I can deal with since I need a LITTLE clearance for driving in the snow occasionally. My bigger concern is, will the springs improve the handling enough to make it worthwhile, without killing the ride back and forth to work?
3) Next is the front sway bar. I have read absolutely nothing about this, other than it's a lot more difficult to install. Any input?
4) Last is the Rear Chassis Member Brace, which I assume is similar to the sub frame connector I put in my 02 Camaro years ago. Although I have read nothing at all about this, the sub Frame connector made a significant improvement on the Camaro. I just don't know if it's really the same, or not. Any input?

Lastly, I'm not really interested in coil overs. I like improved handling around town, but I'm not going to autocross or anything, and it seems like that's going much further than I want.

Any input is welcomed!

 

I didn't think installing a front sway was that difficult. Time consuming because of the plastic you have to remove underneath, but not that difficult.
lexus sells the rear sway by itself but not the front (not that I could find anyway), so if you buy the rear and decide later you want the front you'll have buy used or buy the rear again. They aren't that expensive so I'd go for both if you go for either.
Dropping the car by itself lowers the center of gravity and therefore will improve handling regardless of any other change. My car came with tein s.tech lowering springs and I switched to coils precisely TO handle the snow. I raise it an inch and a half or so in winter, otherwise I'd never get down the alley some days. I do that the same day I change to winter tires. It is a pain, but doesn't take THAT long. Just food for thought.

 

In YOUR case here, you best bet would be the sway bars AND a dedicated set of summer and winter tires. Surprisingly a mod of your tires nets you the best all-around gain in performance. :

 

Bagg um, enough said!

 

I'd say get the sway bars (both) there's different opinions on weather the front is worth it because it's not much larger than stock (I bought both). Start there and see if you like that, then go for the springs. I would stop there from what you've said. I had coils and the chassis brace but I don't think you need it.