The 1200G is a bit of a pig to change tonearms on - and there's very limited clearance for the arm pillar vis a vis the baseplate, especially since the platter is so low profile and the arm often needs to come down a long way to get the correct VTA. I did an SME IV swap on one recently (not my own deck) and it just about worked. Though, it certainly did improve the deck. However, I would just upgrade the entire turntable because it's bad value to end up with a redundant arm that doesn't really fit anything else, versus trading in the complete deck for an alternative - there's a myriad of choices.
As has been said, any of the Pass preamps would work well.
I suggest consideration of the Parasound JC3+ phono stage which is excellent value for money on a price/performance basis.