The echo's are my favorite in that range. Consider getting the straight shaft ( a bit more) to be able to get underneath things better and the added length may help in the ditch line for you too.

X2 on the Echo. I have had a GT2000 for many years and no problems. Just install a new plug every spring, start 'er up and go. Use Stabil in fuel.

I'm using a 5 year old Mcculloch weed wacker that I bought new for $99 and it has never caused me even one problem.
My next weed wacker will be an Echo cuz when I bought my new mower back in June I also checked out the Echo line of weed wackers and I was real impressed at how lite they really were.
Honda also has a line of lite weed wackers but they are very expensive compared to the Echo's but if you like Honda I guess price isn't really an issue right?

X4 on the Echo line. We have one that has cleared miles of electric fence multiple times a year for the past 6 years with no issue.

DO NOT buy one that has the pull start on the front of the engine by the trimmer shaft. The ones with the pull start on the rear of the unit have a bearing on both ends of the crankshaft rather than just on the front. Curved shaft trimmers sometimes have issues with the cable because... its a cable and it bends as it turns and sometimes fails. Straight shaft trimmers usually have a solid rod for a drive shaft which is more durable.

Stihl, Echo, Homelite are a few that come to mind to look into.

Echo back in the day made trimmers and saws for John Deere and the only difference was they were painted and stickered Deere. I would say best bang for the buck.

X5 echo echo echo echo echo... Hey is there an echo in here or something?
Seriously tho echo has done good by me.. Stihl is my preference if i had a choice.