If your that worried about the lack of power, why not change your order for an IS300.
I have a mate with a 3.0L Z3, and it keeps up with him 0-60 and then the torque and gearbox takeover and I begin to pull away form him. Hit the bendy bits, and the superb suspension and chassis setup strip the Z3 (the Z3 get's really skitty, and can't handle undulation whilst changing direction).
One of my other mate's drives a Puma Racing, and although he can keep up with me around the bendy stuff, he again gets problems keeping up at speeds of over 90+.
At the end of the day the car was designed to compete in the exec market. It just so happens that it has a wicked chassis and suspension setup, and I imagine (as I'm yet to try it!) would make for a very exciting track day experience.
It also depends on the image you want to project as well.
Lexus :- Cool, understated, affluent man with a lady magnet.
or a "t**t in a cap", rev the nut's out of my little engine, max power sticker'd, small tin box driver.
Also you will find that the rozzer's tend to take more interest in these little tin racers than they do the Lexus, coz they are usually driven, at speed (in a straight line, form traffic light to traffic) by inexperiened drivers.
Enjoy the attention you get just cruising around you fav night spots in your Lexus. Then if you feel the need to race a tin pot get them on to a bendy road or on a motorway, then watch as you quickly wipe the smile off their faces with your superior car (even with only 153Bhp!!)
Have fun, enjoy your Lexus, and welcome to the club!!
Martin