The trans in my 2003 blew out on me, and with 180K+ on the engine, I decided it was time to part ways with the car. I'll share my research/experience with you, opinions may vary, maybe it will help you think through it.
#1) Solenoid replacement on a high mileage 4T65E trans is probably not economical. The reason is because of the labor associated with getting to the solenoids is extensive, and not far off from dropping the entire trans anyways. You hear a lot about solenoid replacement, and how it solves a lot of problems, but in the end, I don't know if beyond a certain mileage if it makes sense to risk solenoid replacement vs. a full rebuild. You still have a valve body and gears that are high mileage.
#2) Bench rebuilds are the best bet cost-wise IF you can drop the trans yourself. It's a big job, and transport to a shop is obviously a challenge. In NE Ohio, I found a reputable bench rebuild estimate for $800 including a shift kit, which I was told will extend the life the transmission. Still, this wasn't worth the time and money to dump into a car that was probably only worth $1500-2000 blue book.
#3) If you look on Triple Edge Performance's site, you'll see in general, these 4T65E transmissions are really expensive, and they really suck out of the factory. There are a variety of problems, including low slip, gear loss, etc - Most seemed doomed for an eventual rebuild/recore - I'll bet the TEP builds are high quality and will last you a long time, provided you maintain it properly. It seems hit or miss in terms of whether or not the one you have from the factory is going to last you. With as many miles you have on the car, you have to decide whether or not it's worth fixing.
#4) I would never recommend taking a junkyard trans, and putting it in another car without a rebuild first. Since you already have a core, you're risking more money/time wasted taking a risk on a junkyard unit. Even with a warranty, do you really want to take a chance having to drop / replace a second time? I've taken this chance a couple of times in my life, and it ended up not working out. Not on my impala, but with two RWD cars, so the drop / replace was a little easier to deal with.
