In that price range, and since you are talking Parker I would say you have a huge range of opportunities.
I have more than half a dozen 51's all well under $200 and almost all of them are fantastic writers. In fact something about these pens seems to me to make them above average performers in my book. The P51 is a slippery slope, I just had a look and I'll just say ... quite a few more than half a dozen.
two of my all time fave pens are a 1945 green pearl Vacumatic (incredibly pretty as well as a great performer) and a 1926 Duofold with a broad stub nib. Both are fantastic writers; think of it, a pen that is 87 years old and works just a well as it did the day it came out of the factory. This is not a pristine show pen, it's a writer but aside from one small repaired lip crack and some brassing to the clip ball and band, this is a beautiful, classic, perhaps iconic piece of indistrial art. The green pearl Vac is one of those things you catch yourself staring at in midsentence in the right light, well, in almost any light for that matter. Both have gold nibs, the vac is a little springy, the Big Red is a nail, but a very smooth nail.
I tell people that Pelikans are my favorite pen, but if I took care to make a close count, I think I might come up with more Parkers.