I'm also 1.80m and ride a medium Prophet (also a 05 2000, sweet bike!). I could probably ride a large but on a bike like that, I prefer a shorter cockpit than a stretched out XC race position. It still climbs like a goat. But forget what I like, nobody can decide for you, try one, sit on one in a shop at the very least. If you really can't, compare the horizontal top tube length with your old/current bike.