I used to have an old Gallagher, had it for years, and worked great. I had it hooked up to almost 2.5 miles of fence. Don't know about the new ones though.
Right now I am using a Zareba SP3B solar charger. Supposed to be good for three miles. I am only doing small sections(4-5 acres) for rotational grazing to save my grass but I am happy with it.
I have a friend that uses the Fi-Shock.(like smrobs) He trades cattle and as we all know that sale barn cattle can be a little unruly and tear your fences up. He puts them cattle into a receiving pen with a electric fence just to the inside to train them. After about a day or two the worst fence crashers will abide by that Fi-Shock!
The key is to have a good ground! I have three 5ft. copper ground rods sunk and keep that ground wet.
Also I was looking on the Zareba website today to see if I could order parts(I lost the little plastic screw on caps for the posts) and they have a really cool thing where you can type in your address, it gives a satellite picture of your property. You mark the corners of the piece you want to fence, answer a few questions and it gives you a list of the supplies that you will need to make it happen. I thought it was fun I played with it for a good hour today.(I am a dork...lol) You can order those supplies online, but you could just take the list with you to your nearest farm supply store and get them cheaper I am sure.
Best of Luck!
I DON'T LEAD 'EM AND FEED 'EM, I RIDE 'EM AND SLIDE 'EM.