Pi314,
If you cannot set the dish back further to the north to overshoot the trees like Anole mentioned, then you'll have to go with RG-11 cable and possibly trim some branches or remove a tree.
Although removing an entire living tree just to get satellite reception is not on my list of positive approaches to resolving the issue, but a little selective trimming isn't too bad.
With the RG-11, you can get your dish set out further south quite a long ways and reduce the tree trimming venture.
You can easily get to the 300 foot mark with quality RG-11 cable and secure a strong signal quality level. I believe that you will be even able to reach the 400 foot mark without any amplification means at all.
I have run RG-6 cable to 200 foot and had no problems with signal quality even though I could detect a slight drop, but I did start to develop trouble operating my H-H motor due to DC line losses. The further I went with the RG-6, the more I could detect degradation of the signal quality, but that was not my immediate concern as there was still plenty of headroom remaining for my receiver to lock onto the signals, it was the motor control issues that were my main trouble. Beyond the 200 feet, I almost couldn't use my motor reliably with RG-6.
I've never been very keen on the in-line amps, so I won't address that application out of lack of personal experience.
As for the channels (major networks) that you want to pull in, you'll have to go C-Band.
RADAR