Woohoo! Successfully upgraded from stock Gingerbread (rooted & S-Off) to Virtuous Inquisition ICS! I wrote down what I did, so if anyone is interested, below is how I did it. It took about 15 minutes in total (not including the backups). Hopefully it helps someone else out there!

1. Titanium Backup all apps
2. Nandroid Backup via ClockWork Recovery (1434 MB)
3. Get CID Version:
   
   1. Download ADB/Fastboot files from attachment from Post #1 of the [Firmware][Mar 12] thread
      
   2. Connect phone to PC -> adb reboot bootloader -> Then in bootloader:
      fastboot getvar cid: T-MOB010
      fastboot getvar mid: PG5810000
      fastboot reboot
      
4. Download the appropriate Firmware from above thread (CTRL+F for T-MOB010/PG5810000) and the Virtuous ROM from Virtous Website
5. Copy both files to sdcard, check md5 on both
6. Flash Firmware:
   
   1. Turn phone off -> Hold Volume-Down + Power to enter bootloader
      
   2. Wait for the firmware package to be found and confirm to update as prompted
      
   3. Once completed successfully and asks you to reboot, pull the battery out. (Gingerbread & firmware are incompatible, causes bootloops)
      
   4. With phone off and plugged into PC, do adb reboot recovery (Thanks pyrilium!)
      
   5. Mount USB storage
      
   6. Use PC to delete firmware file from sdcard
      
7. Wipe all data and cache -> Flash Virtuous -> Reboot

(Note that YES, flashing firmware causes bootloops -- as I found out! So firmware and ROM must both be flashed together.)

And thanks pyrilium for the note about using "adb reboot recovery" while the phone is off! I would have never figured that you could issue adb commands with your phone off. That tip isn't even in any of the guides, so thanks for that! Extremely helpful.

Anyway, hope that helps others out there. And thanks for helping me!