Yeah, tape head alignment is the same thing as calibration.
It can make a huge difference in the sound quality and reliablity of your tape heads and is often overlooked.
For A/D conveters, I currently employ the converters on
my TC Electronics Gold Channel. It's a 2-ch mic pre with analog ins and outs and spdif, tdif optical, and AES/EBU ins and outs. In addition to it's nice mic pres, it's got some really nice A/D conveters, especially for the price of it all ( i got mine for around $800 used). Initially, I was looking to buy dedicated A/Ds, but I also needed some nice mic pres and the Gold Channel was the obvious choice because it had both (plus a bunch of other cool features). If I had the cash, though, I would have bought
the Apogee Rosetta 200 (2-ch. 24bit/192khz A/D and D/A) and a Universal Audio 2-610 dual tube mic pre. Apogee makes the best A/D converters, in my opinion. But I tested out the Gold Channel and I was happy with everything it had and the price was just right. I also had my eyes on the Lucid 9624 stereo A/D converters. These are a bit cheaper than Apogee's and offer comparable conversion quality (not quite as good, but still way better than the A/Ds on a digi002). Any other converters I am not too familiar with, but Lucid and Apogee are two very good names to know. What's cool about nice A/Ds is that it can bypass any crappy recording interface you have. At my apartment, when I'm recording demos and testing mics etc. I use this Lexicon Omega interface. It's a dinky little 4- ch USB interface with some A/D conversion that just doesn't cut it for me. But, it has SPDIF ins and outs. That way, I can record everything through my Gold Channel and it's like the Omega was never there. Same goes for my digi002 at my studio; i can bypass the crappy stock converters and it's like you never knew it came through the digi002. Once again, quality A/D conversion can make a huge difference in your sound. It makes all your other equipment (mics, instruments, fx, etc.) sound much better than you thought they could.
About reel to reel tape decks, I don't know a lot about them. I've worked with them a lot, but it was only a few select models that I used over and over and over again. From my limited experience, I did notice that Studer is probably the best tape machine company out there. I never had problems with Studers and they were always in complete working conditions, while other brands of machines usually had something wrong with it (fostex, tascam, even otaris). They are a bit pricey, especially the 24 track machines, but you definitely get what you pay for. The 16 track machines are pretty expensive too (unless you're thinking of a 1/2" fostex or something). Really, what I would suggest is getting a 2-track mixdown deck. Studer and Otari make some great 2trk 1/4" machines that are going for good prices all the time on ebay. I'm on the verge of getting one myself, but I'm waiting for the right deal. Revox/Studer probably has the best models out there for 2trk machines. They aren't nearly as expensive as a 16 track or 24 track and you still get all the nice analog warmth. You can record your track in Pro tools or whatever and mix it down to 1/4" 2-track. This is a very common proceedure when recording major label records. You can still get that analog sound with all the benefits of tracking and editing in pro tools. Plus, it's a hell of a lot cheaper to get a decent 2trk machine (although you can still find some damn expensive ones if you look) and 1/4" tape is much easier on your wallet than 1" or 2" tape. Anyways, look for Studer, Revox, and Otari. Those are probably the best tape machine companies around.