I've got a rode nt1a going through an Mbox 2 Mini (USB) I'm wondering how much better the sound quality would be if I upgraded to the Duet? Or would I get better sound by getting the Joly mod on the NT1a instead for the money? Hmmm...
You won't regret buying a duet over your mb2. That is for certain. I bought an mb2 mini for my home setup just for putzing around and hated it. The duet 2 will also allow you to hook up any 2 channel mic pre you may purchase in the future as well.
Yea the duet will sound better. I am more of a mic guy though and would want to get another mic. All depends on your scenario, but in my eyes a mic will last, interfaces come and go. In 2 years you will still love your mic collection, but covet a new interface.
The Joly mod is great, my modded NT1 sounds like a new mic, I'm very happy with it. On other hand, it's pretty hard to love the Mbox preamps, so upgrading them would be a good idea when you can. I'd go for the mic first but either one would be worthwhile.