I hope you don't mind if I jump in on this conversation as my theory's might not prove much but just something else to add.
I've switched interfaces...and microphones before. there is a lot of mind games that happen.
its almost as if you have to retrain your ear all over again. especially if your previous interface was a cheap one.
this has happened to me a few times in my life, back in 1986 when I first started recording (no old jokes please=I was a young teenager) I had an old Tascam 4 track reel to reel and the highs were spectacular. so much I got used to cranking the snot out of them leaving all my mixes baseless. no low end at all.
it wasn't till 1991 I got a nice desk and a very helpful engineer (Ed McGee from Boston) helped me train my ear all over again. then it happen again in 2000 when I bought my first audio interface for a computer when the digital audio movement started. I bought a crap interface with crap converters. when I finally got a good converter (interface) I had to retrain all over again.
FIRST-Re trace your whole signal path. from your speakers back to the input. if need be, plug in your old interface to compare. take special note to what you are using to monitor on, the speakers, headphones. are they plugged in to the same jacks as your old set up.
what you might be experiencing is the mic pres that adds some color to your signal.
a good color. you need to learn to dial that color in.
this new Mid range that you are hearing can very well be what your old set up was missing, your just not used it.