A higher stall torque converter will make your car "feel" more responsive and fun to drive, and you don't have to go crazy with the stall speed to get there.
I bought a 3500-3800 stall converter for my first MKIV Supra and it literally transformed the way the car drove. The 2JZ-GTE motor is a fantastic engine as long as the RPM's are kept up, and it's on boost, but much below 3000 RPM, in an A/T car, it's a real dog. The higher stall converter helps keep the RPM's up, so the engine feels much more responsive.
In your case, if you're roadracing, you're probably frustrated when the engine bogs down in the low RPM range, probably when taking a tight corner, and the tranny doesn't downshift fast enough? The higher stall converter will help this a lot.
For daily driving, the change isn't too obtrusive, unless you go nuts with the stall speed. 3500 is probably plenty, and you won't have to give up too much of that cushy Lexus launch.
The downside is that there will be more heat generated by the tranny and torque converter, so you should plan to run a good sized transmission cooler, and don't let your ATF go too long between changes.