A modern deck like the GR-1 you mentioned will be better than the old Dual's out of the box although these are worth a look if you are on a tight budget and can get into tweaking and install your own modern tonearm, if this is possible. The Dual CS505 is also a great budget deck as are the Pioneer PD112, Sansui SR222 and NAD 5120 although these are not really upgradeable.
Thorens TD147/150/160/166 are probably the most tweakable old decks going as the arms are easily replaceable and upgradeable.
A Thorens with a stock arm out of the box will be the equal of the MH / GR1's and with some tweaking (better arm, new plinth, service) will take on all comers into the 2000USD territory and beyond.
The only drawback with these Thorens is that the suspension is a bit too springy for the Rega RB250 which is THE budget tonearm par excellence and forms the basis of most moren budget (-1500USD) decks. The high-end Thorens like the TD125/126 can take any arm and are much better built if you can find one.
The Technics SL1200/1210 can take an RB250 arm as mentioned and this makes it a serious contender as the level of build quality is superb. Far better than any of the other decks mentioned bar the more expensive Thorens.
Don't believe the hype about direct-drive not being audiophile. A Technics 1200 / Rega RB250 set-up will wipe the floor with any of the MH, Rega Planar 2 / 3, Project, Goldring GR1 type decks.