My two cents, for what its worth. I have most of the pens previously mentioned, and then some: Pilot Vanishing Point (4 of them now, I love these pens), Pilot Metropolitan (my first FP), Lamy CP-1, Lamy Studio, Lamy Safari/AL-Star, Lamy 2000, TWSBI 580 Diamond, TWSBI Eco, Kaweco Lilliput, and more. Lots of pen, but few of them would be in your desired price range.
Pilot Vanishing Point: Way outside of your desired price range, but there's a reason I have 4 of them: it is a f**king awesome pen. No ifs, ands, or buts about it. If you can ever get one, DO IT. One of my 3 daily drivers. Get it in matte black for a very stealth look.
Lamy Studio: The 2nd of my daily drivers. Very smooth in medium. Excellent pen. My only gripe is that the grip feels too smooth some days. It is something others have commented on as well. The grip is perfectly smooth, untextured metal, so you may wish to try it before getting it.
TWSBI 580 Diamond: The final daily driver. As a piston filler, massive ink reservoir. I love this pen to bits. Should be right at or slight above your desired price point. May be considered a bit more showy than the Studio, with the clear body that shows off the ink and all. Be careful if you disassemble it, reassembly can be tricky, but there are videos on youtube to help with that.
Lamy CP-1: If fountain pens are too big for you, this is the pen to get. Roughly the same diameter as your average ballpoint, this pen blends right in. Lamy nib, which means it writes just as smooth as the Studio. I found mine in EF too dry for my taste, but that sound like it would be right for you.
Lamy 2000: Mostly for future reference here. I have a love / hate relationship with this pen. Very smooth nib, if you can keep it in the sweet spot. Keeping it in the sweet spot though, is like trying to balance a pen on the end of your finger. Not something easily done, and compared to the TWSBI 580 and the Studio or CP-1, not something I will spend the effort on, as nearly every other pen I have is far less finicky.
TWSBI Eco: Comparable to the Pilot Metropolitan with regard to price point, roughly 20$ or 30$. The least expensive piston filler I know of. Personally, I'd skip it and go straight for the 580, since the 580 feels far better in hand, but a decent pen still.
Inks: My daily drivers are used at work, which require waterproof inks, so Noodlers Bad Blue Heron in the Studio (nib creep is a thing, but the Studio is easy to clean) and Noodlers Liberty Elysium in the TWSBI. I have Pelikan Edelsten Topaz in the Pilot VP for everything else.
tl;dr: Get the TWSBI 580. Save money. Get the the Vanishing Point later.