Suitable rear mech for Megarange cassettes I just bought an 11-34T 8 speed rear cassette and noticed that it is a Megarange cassette with a substantially large jump between the lowest and 2nd gears. 

Will this work with my existing Alivio rear mech or do I need to get a different one? (Such as in this question here)
It will probably work.  The one thing you need to look at is the length of your derailleur cage.  With that really large cog, you might have to adjust your chain length, and then your derailleur might not be long enough to properly tension the chain.