Mmmm.. tuner questions. My favorite. I'll give you my every couple of months tuner marathon post. It's an area hi-fi mags don't talk about, reviewers don't know about, and where new vs. old means next to nothing.
I'm not totally sure what you're after here: If you want a good sounding tuner, scratch a stock MR78 unless you get Rich Modafferi to go through it and upgrade it. Lots of parts are going to be way beyond life expectancy and probably need replacement for best sound. If you're trying to pull stations from 70 miles away, buy the Mac anyway, because it'll do that better.
That said, avoid the Magnum's at retail as well. You're buying a nice faceplate and power supply attached to a marginal tuner with the MD-100, and the same attached to a slightly better tuner with the MD-102. At these prices in this era, we ought to be seeing a balanced mixer, multiple group delay equalizers, GaAs FETs in the front end, and an analog multiplier MPX, but we're not.
If you want to save some cash, buy the Rotel RT-990BX advertised right now (or RHT-10 on eBay). This thing uses audiophile parts, and is a *MUCH* better design than the MD100 or 102. The FM stereo multiplex design is among the best ever, and is basically a knock of off of Yamaha's design in the T-85, TX-1000 and TX-2000. Actually, the Yamaha's are even better than the Rotel from a design perspective, but not quite as good in the parts arena. But in FM, if you screw up the design, particularly the filters, all the parts in the world won't do squat. These are not preamps. From a design standpoint, the Yamahas are really some of the best ever. If you don't mind swapping out about 10 capacitors, buy a Yamaha.
I also recommend the Nikko Gamma V and Sansui TU-X1. The Gamma V is a remarkable design that has just about the lowest levels of THD and IMD that I have measured to date, and is one of the most overlooked and undervalued tuners you will find. I have measured this tuner personally at .009% or less in stereo to over 10kHz, and I've aligned and measured dozens of high end tuners. Also consider the 40 lb. monster Sansui TU-X1 if you're in the "around a grand" price range. It really is one of the best designs ever (if you really want to know why, I'll tell you), and I don't doubt anyone who claims it is the best sounding stock tuner they've ever heard. I just bought one, but it hasn't arrived yet. [If anyone considers this, make sure the "japanese" one presently advertised is USA band. I suspect it is not.]
Finally, even if you buy a new tuner from Magnum: If you want to listen to this thing instead of just stare at it, GET IT ALIGNED by someone good with proper equipment. That does not (IN MY OPINION) include your local TV guy or a certain former Stereophile reviewer, for various reasons. Doing a true high end unit requires a sophisticated RF generator with intrinsic distortion below .005% and a MPX generator with 70dB of separation. I use a Radiometer or Panasonic setup that has no problem with this. Hint: Most Audio and TV repair places do not have this stuff. It costs too much and is too limited-use.
So, whatever you decide, good luck. I assumed you wanted something big and meaty and high-end looking, so I left out a huge list of good, cheaper stuff, or stuff you just won't find to buy. (Accuphase did some nice high-end looking stuff too, but its hard to find). Everything I mentioned is presently available on A-gon or eBay, at least for the moment. If you want the list of cheap looking stuff that's just as good at Magnum or Mac, just ask. But if you're after pretty, the Magnums certainly do well there.
I know this didn't really answer your question per se, but I hope it helps. The MD-102 isn't really that bad (so I've heard), but you mentioned the high price, and I agree there. I also threw the requirement for an alignment at you, which I'll hammer out more fully if/when I decide to offer this service on A-gon. AFAIK, no one else with proper equipment has offered this as a standalone service, which bugs me, so I intend to fill the gap sooner or later. Suffice to say my Gamma V went from .2% THD down to .007% at 6kHz, and that is not really an extreme example, although how low it got obviously is. Hope this helps you in your decision.
