At that price range you have PLENTY of banjos to choose from. That's the fun part!
As far as what you're looking at, I have a little experience picking around those. I've never played a Washburn B120K, but I do own a Washburn B19. I think they are pretty comparable. The B19 was Washburn top of the line banjo in the late eighties until '91. In 1991 it retailed for $729. I like the sound of it, but to be honest with you, I wouldn't have paid that much for it. I found it on ebay for a much lesser price.
The other day I went up to a banjo store and just sat and picked on about every banjo they had. The Fender FB-58 was one of them. I was actually quite impressed with it. It's tone was much brighter than I though it would be. Whereas my B19 has a pretty mellow tone. The build looked and felt like a very quality built instrument (i.e. actually felt like it was made out of something real, not pressed wood shavings).
I know nothing about Morgan Monroe Cascade Banjos.
However, I do want to throw one more in here. While picking that day, I picked up a Recording King R35. If I had the money, I would have bought one on the spot. In fact, I had my Washburn with me and tried to trade it in for it, but they said they weren't looking for trade-ins at the time. The RK35 far outplayed anything else I picked on (other than the $1,500-$2,500 banjos). I came home and did some research on Recording Kings, and apparently they are doing something right because they're getting raving reviews left and right.
Whatever route you choose, we're eager to hear!