Ok guys, here's the deal.....
Since I've already successfully modded one Xbox (Xenium Ice 2/120GB HDD), I've decided to add a box to my arcade and use it to play STRICTLY shooting games from 8 and 16bit consoles (NES, SNES, SEGA, etc...) and Xbox titles (since Actlabs went bust on the light gun). 
Here are the stipulations:
1. Will be modded using the same Xenium Ice chip
2. Min. 40GB HDD
3. Use KTM/AV switch for audio and video to go between MAME and the Xbox 
4. Run all games from the drive
5. Do it all for under $150
Planning:
This should go fairly simple. I dont need a new Xbox for this project, as a matter of fact, I can get most of what I need from 
http://www.fixmyxbox.com and 
www.ultimarc.com. 
Parts needed:
* Version 1.0-1.5 Xbox mobo/w PS                (Free-$50) 
* 40 GB HDD                                                   (Free)        
* Modchip                                                       ($50)
* Xbox adapter(s) from Ultimarc                     ($40-$60)
* AV switch                                                     (Free)  
Thoughts?