Whereabouts are you? Your local farm retailer should probably be able to advise you a bit.
I've just got a stihl 361 to replace my aged ml310. The 361 is a little less torquey than the old 310, but much lighter and still more of less as powerful.
That said, the 361 will happily run an 18 inch or even 20 inch bar, and from what you've described, that make be severe overkill for you. I'm not sure on the 2 models down from a 361, but if I were you I'd probably find the stihl saw options which are shipped with 14 inch bar as standard. You won't need more than that for a bit of hedge and coppice work.
Someone will be along shortly to tell you about chainsaw courses no doubt