So I've been blessed to be able to own some pretty nice hardware gear over my time as an artist/engineer/producer/beatmaker. I've had some that was fantastic and I've had some that weren't so much. I'm gonna talk about my favorite ones the I own(ed).
Audient iD44: This is by far my favorite interface so far. Not because its my latest one, but because I truly hear a difference in the sound quality for the first time. I've said that with other interfaces I've used, but the honeymoon would usually be over by now. This one is the real deal. I was debating between this and the UAD, but after doing my homework and research I figured this would fit my process better and so far it has done the job
Mbox: The very first mbox by digidesign will always be a classic. What I loved about this were that the focusrite preamps in it were killer. At the time I was amazed that I could get a good clean vocal recording out of this. Now true enough when I got this I was just starting out recording on my own so I really didn't get to push this to its max, but I've kept mine because in a pinch, you'd never know when you may need it.
Mbox 2 Pro: This was still when you needed digidesign interfaces to use Pro Tools. So glad they've made Pro Tools available for other products. I got this on ebay, but it suited what I needed. I was making beats on the MPC1000 at the time and badly needed the extra inputs. So this worked out well for me, but I missed the focusrite preamps.
Akai Professional EIE: To be totally honest, I do not remember the reasoning for me buying this interface lol. I'm sure it was for podcasting reasons, but I didn't start really using it until last year. There isn't anything mind blowing about it, but it is does the job that I need it for. I wouldn't use this for music recording at all because the sample rate is basic and I like recording above 16 bit/44.1k, but it has been reliable for me as I'm using this for podcasting.
Mackie Universal Control: I wanted the digidesign Command 8 SOOOOOOOOOOOOOO bad, lol. A friend of mine had it and it made mixing so easy for him. I was used to mixing on a board so when I started engineering on my own I missed that control. Using a mouse was a headache for me and it wore me out. What I love about this is the functionality across DAWs. I can pretty much use it with whatever I choose to use. I can also expand it if I choose, but I think I can pretty much handle the way I have it now...for now.
Korg nano-kontrol: I use this to record and mix my podcast. I use my laptop and the Akai EIE for podcasting purposes and it really is a viable option. I used to use it before I got the MCU as well, but it was pretty limited so I had to upgrade. But as a portable control surface it pays for itself.
Headphone Amp/Preamps/Channel Strip:
Presonus Studio Channel: This has been a gem for me. It not as fancy as some of the others you may see out on the market, but I replaced the tube in it and it has worked wonders for me. I don't use the preamp in it anymore because of the pres that come with the iD44, but when I was using when I had the MOTU Audio Express it worked like a charm. The EQ and Compressor on it helps bring in a good signal so that mixing on a vocal isn't as time consuming and tedious as it once was. If you're looking for a good strip to start out with I'd suggest this one. It is still holding well for me to this day (word to Deontay Wilder).
Presonus TubePre: When I went over to the MBox2 Pro I wasn't as fond of the pres that were in there as I mentioned above. When I bought this the salesman at Guitar Center suggested that I switch out the tubes that were in there with some Russian tubes that were sold at a place in Midtown Memphis called Xanadu. I bought the last two and I couldn't have been more satisfied. They really helped while working with the MB2P and the MOTU Audio Express.
Presonus HP4: I love this, but I don't use it anymore for the time being because the iD44 has two headphone jacks to it. I bought a smaller headphone amp to use for podcast recording, but the is much more versatile. Its still can be a valuable part of my setup when needed.