You don't need a modchip to play backups, emulators, and run homebrew apps. Just snag any old Xbox, throw in a bigger hard drive, and you're good. I'm oversimplifying, but it's a softmod, and there's plenty of YouTube tutorials out there. It's pretty easy to do.
It is really easy. I did a few last year. Just needed a certain version of Mechwarrior, one of the Splinter Cells (forget which), or another game in forgetting.
It's WAY easier than installing a mod chip, and it's much more likely you'll find either an unwanted Xbox that can be modded than a pre-chipped console. If this info isn't helpful, then no prob!
The softmod is easy, but you need a special cable, and to find the right vintage USB memory stick and version of a game. If you don't already have Splinter Cell, everyone should have it in their collection anyway.
Reminder to anyone who owns an OG Xbox: remove the clock capacitor and re-cap that shit. That thing is a ticking time bomb that will murder your motherboard. I lost two modded Xboxes to that damn thing.
You can readily get pre modded ones loaded up with games and emulators on Etsy and eBay. Heck, seems like you can get a modded 360 these days with a multi terabyte HDD full of ogxbox and 360 games. That might be a good alternative since you get both libraries and a more powerful system for console/arcade emulators.
If you're still looking I have one I may consider selling. It's a Japanese launch model with a smoke colored case. Has a mod chip, HDMI mod, upgraded ram and larger HD installed. The DVD drive doesn't work and according to the installer the console is locked to 480p.