You've got a lot to consider. I'm a lawyer as well, and use my fountain pens in a variety of settings and for a variety of purposes. Some are very conservative in appearance, some less so (though none would be considered gaudy - I hope!).
You've gotten some good advice here already. Specifically, the M2XX series by Pelikan is an outstanding pen and a very good value. As others have pointed out, they are a little slimmer and, in my experience, a little uncomfortable for a larger hand. One issue that's not been brought up with this pen is the location of the threads - they're a little high for my taste and tend to irritate me when I write with it. Of course, everyone's hands and tolerances are different, and it may not be a concern to you at all.
Aurora pens are wonderful! I've been very happy with the Aurora 88s I've used, but I confess I have no experience with the Ipsilon series. Aurora is a respected brand, though, and I'd be confident in their quality. Their nibs tend to have a little "tooth" to them (but they're not scratchy). Some people prefer that; others want their nib to skate over the paper without the slightest hint of feedback. Again, YMMV.
In your stated price range of $80-$150, one of my favorite pens lately has been a Cross Affinity. It doesn't meet your piston-fill requirement, but it writes wonderfully, and has a classic look to it that would make it at home in any law office.
Many people love Lamy. I'm not among them. Don't get me wrong, I don't dislike them, I just think there are a lot of better pens out there.
The ink-vue window does tend to limit your choices. Can I ask why you prefer a piston-fill pen? Is it because it is more classic? Is it capacity? Because you want to use bottled ink? Or is there another reason? If it's because you prefer to use bottled ink, most pens today can accept either ink cartridges, or a device called a converter, which permits the user to draw ink from a bottle. If it's capacity, there are definitely merits to the slightly smaller capacity of an ink converter, not the least of which is you get to flush your pen out more frequently, and you have an opportunity to experiment with more varieties of ink - if that's your pleasure.
Also, I noticed you've been getting many suggestions for a fine nib. I find that nib choice is greatly dependent upon the user's intended use for the pen. For example, a fine nib is perfect if you want a general purpose pen with which to take notes or write correspondence. But if you want a pen for to sign documents, a fine nib may be a bit anemic. Bold nibs (and italics, cursives, music and stub nibs) are very popular choices for signatures - and with good reason. Particularly the italic-style nibs referenced in my parenthetical create far more line variation, which gives your signature an unmistakable flair that distinguishes it from more ordinary "ball" shaped nibs. If that is appealing to you, you may want to check out pens by Sailor and Platinum. They may be a little higher priced, but their nibs tend to be extraordinary. A Platinum music nib is a real treat!
And never hesitate to ask a retailer to special order a pen for you! Odds are, if they don't have it in the store, they can get it for you. If they're not willing to do that, I'd take that as a hint about the quality of service you can expect in the future.
Hope that was helpful - and congratulations on joining the noble profession!
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