Here are two old PMs that helped me decide on the Vegh from DavidW. I believe I posted them before, but thought it worthwhile to unearth them again:
It might be very annoying to read my posts on Beethoven SQs because on most of the threads I just get into brawls with other posters. What can I say, I'm a jerk!
Fast--
Smetana Q (supraphon) but you have to get these from Japan!
Juilliard Q-- you have to get the whole box set to get these I think
Talich Q-- again I think you'd have to get the whole box set
Slow--
Vegh Q (second set, stereo) oh no another box set!
That's for the late quartets, for the middle ones that you're missing I suggest the Takacs Quartet. If you go for the Juilliard Quartet they're just as good IMO. Also I like the Vegh Quartet there as well, they are on the slower side though.
and this one:
For Supraphon they only did only one of the early quartets. So if you want the Smetana Quartet, you don't have much of a choice there. I haven't heard the denon recordings myself.
My favs for the earlies are Vegh Q and Takacs Q.
You get the pattern I have here-- if you don't need speed, the Vegh Quartet's emotional depth is profound. The Takacs Quartet are exceptional, but swift. They are perhaps the most modern cycle. Like Todd I like what they (Takacs) did with the late quartets, but there is so much fantastic competition (at a lower price I might add!) that I have clear favorites above them. However they are nearly unbeatable compared to even older recordings in all of the other quartets imo.