You just need a standard road triple derailleur for a 12-25 or 12-27 casette. I run a 50/34 in front with 12-27 in the back, and this gets me up anything in the texas hill country. For loaded touring or real mountains, I do have a 11-34 casette, but as I said I really prefer the 12-27. If you have a 30 in front that is plenty low when paired with the 27 in back. When you look at the ratio charts, don't think about shifting between rings in front as much as choosing a front ring, and then shifting up and down the back, which is the modern style with 9-10 speed rear casettes. You will probably just wanna be in your 50 for flats, shift to the middle if it gets hillier and to the granny when it gets really nasty. Also, its important to get over the idea that you will fix up your bike to do one thing and one thing only. While I have my 12-27 for *most stuff*, I have a touring wheel with an 11-34 that I can put on my touring bike (which does have a long cage mountain derailleur) when I need it. Once you learn how, swapping casettes is also an easy option. I personally think a mountain rear casette is overkill on a modern light triple. I need it since I only have a double.