I'm piecing together a (mostly) 9 speed Chorus group. The cranks are 10 speed, but everything else is 9. One of the only things I still need is the front derailleur. Sheldon says it doesn't really matter but that makes me a little nervous. Should I go with 9 to match the shifters or 10 to match the cranks? Would an slightly older 8 work? Does it matter at all?