Still setting up, preparing to start recording. Settled for Reaper as my DAW, and have the Behringer U-Phoria 204HD for my Audio Interface.

The one thing I dont have, is a DI Box. I keep seeing people mentioning that its nice to have, or that its a must have.

My recording setup, I plan on going thru my 6505 MH, which has a Mic Simulated Direct Interface on the back. I could also use my Shure 57 and mic up. Either way I decide to go, from there I will plug into my AI and then that plugs into my computer.

FOR EITHER SETUP, the Mic Simulated Direct Interface or the Shure 57, do I need or want a DI Box?

When using the 6505MH, you can plug the USB out directly to your computer. No need for the audio interface. And, no, a DI box isn't needed for recording from a mic into your audio interface. A DI box might be useful if you're recording dry, but it doesn't sound like you'll be doing that.

+ to Rammikin comment; I checked your interface and it has an inst. selection, if you'll ever want to connect dry guitar just select "inst." and you'll be fine.

So since I can go usb straight to the computer, does that basically rule my AI worthless? Are there any advantages going thru my AI vs USB out?

It's not worthless, you'll need it for microphones. Direct USB is better than going through your audio interface since it reduces the number of conversions.

Good point You can skip the DI and just go USB. It will provide speaker simulation as I understand. Otherwise, if you did try for a DI box, you'd have to do speaker simulation inside your daw using a plugin for cabinet simulation. All this assumes you are not trying to mic a cabinet. You don't need DI Box for that, just a mic and an audio interface which would also probably connect via usb All in all, the simple thing is just to connect via usb per RAMMIKIN.

Todd