The stock set-up works great if it's in 100% perfect. No reason to go any further really. If you have an XFI, you can buy Cal's 2-step module and program the launch and redline RPM through the tune. Worked for me and 100's of others well into the 9's and 8's. Some even in the 7's I believe.
But if it begins to give you trouble, and you don't have access to, haven't had any luck with, or care to bother with replacement parts, or just want something different.........
Then the TR-6 can be used with an XFI or a stock computer. Lots of features. mostly plug and play, Indicator lights, dip-switches that change functions, coil-near-plug (or individual coils in stock location), harness can be made to accept GM coils of all kinds, including aftermarket coils like the Holley's, flash updateable, 2-step and rev limiter..........so on and so on.
I think the XIM can only be used with XFI only, (I could be wrong). You would then be able to use all the features in the XFI for ignition programming. Also you will need to go coil-near-plug/individual coils.
Then of course, there is always a distributor set-up with an ignition amplifier. Old school, but still effective for many.
I'm sure many of the aftermarket ECUs have ignition harnesses and logic programmed into their software than will adapt to our application when used on our cars.
I personally thought to use the stock ignition forever. But for one minute it gave me trouble. I quickly used it as an excuse to convert to the TR-6. Fabrication for my custom application is currently underway.
