The Orbe is usually partnered with an SME series iv or v arm it seems to match perfectly, if funds dictate then their own Tecnoarm would be a fine choice. When ordering the dealer would ask which arm you would use and order the appropriate arm plate either an SME fitting or the Tecnoarm plate. I had a gyro SE with an rb 300 arm, set up is not to difficult but i have never set up an SME arm so cant answer that one but i would imagine spending that amount of money the dealer would be the best person to ask. As for cartridges the ortofon kontrapunkt series seem to match well with the SME or something form the Van Den Hul series but again the dealer would be the best person to ask.
i have run my Orbes with SME ,Rega derivitives ,Hadcocks,morch and Graham arms at .present i am using a Mission 774 none of the arms i have tried have been a problem as Michell will make a custom amboard to suit your choice. John Michell developed the Orbe with the SME arm as his standard so its fair to say that a match is there.As with all hi fi i would always say you get what you pay for so go for the best you can afford at the time as the and up grade when you can.
cartridges ,as already stated are a matter of taste but again "yer pays yer pennies"
out of interest i am making a 12 inch arm tube for the Mission that should give the guys at Michell some head aches.