The first thing I'd do is give the tape path a very thorough clean. Dirty heads while recording can cause dropouts and a dirty capstan will cause the warble. If you are trying to use Ampex or Quantegy tape then stop - you'll only gum up your machine with as it sheds sticky residue everywhere.
Try putting a tape that you've recorded on backwards (ie, swap the take-up and supply reels). Do you now hear a backwards version of track 1 through track 8?
As Dave says, the HA400 works fine with high impedance headphones. So do all the other audio interfaces that I've tried (RME, Focusrite and Zoom) although I've not used the MOTU ones. I usually buy high impedance headphones because I have one or two old bits of gear that need them.
When the C1000 first came out there wasn't that much competition. You either had the £20 condenser mics from the likes of Eagle or Altai or you had mics like the C451 or SM81. Most of the decent alternatives were more expensive but the slightly larger size of the C1000 made it look more...
You are using the wrong type of cable. You need a TRS to TRS cable. The cable you are using is sending a line level signal from the mono out to a mic level input on the Focusrite and overloading the input on the Focusrite.
Does the same thing happen if you use headphones? Are you using direct monitoring (the control nearest you)? Is input 1 working as expected? If so then it looks like you have a faulty U-44.
Not total hogwash. The big issue with the Neumann capsule copies is the tensioning and consistency. According to David Josephson, Neumann's tensioning method is a closely guarded secret and, certainly when he made those comments, the Chinese capsules often sounded nothing like the Neumann ones...
Do you have Intel graphics in your system as well as Nvidia? I had a few odd graphics glitches until I set my default graphics adaptor to the Intel one instead of the Nvidia one.
To my ears, Sennheiser HD600s sound close enough to the Tannoys to allow me to make similar mixing decisions on either. The Sony 7506s have a reputation for sounding very bright - some people like them but they don't sound like Tannoys.
As I understand it, once he's got it configured, it doesn't need to be connected to a computer again so the disappearance of Firewire doesn't matter. That's how I use my Focusrite Saffire Pro26io these days.
Audio interfaces have had built-in DSP since the days of the Turtle Beach Multisound in the early 1990s. Not all of them, of course, but a significant number have DSP in the interface.
I would have to say that some amps do have a sound. Unfortunately the first amp that we used the NS10s with in the studio, a Teac AX75 had a slightly bright sound that made the NS10s sound even worse than they really were. The amp and speakers came as part of a recording package from Thatched...
I think the sound of a Scully or Studer might actually be too subtle for most people wanting analogue "warmth". A Portastudio comes much closer to the sound of tape that people who've never used decent tape machines expect.
The best thing to do would be to stripe one of the tape tracks with timecode and then feed that timecode to Reaper so that the drums play in Reaper while your other tracks play from the Portastudio. If you want the tape sound on the drums then I would record the drums in stereo (or even 3...