I would go with either the ORB or Brushed nickel, but definitely not the brass.

We live in a house built in 1997 and are making many of the same updates. We ended up going with brushed nickel door knobs and hinges. I made the choice after looking at new lighting for the bathrooms and deciding that I liked lighter look of nickel over the darker, more formal look of ORB. In some rooms I mix in black iron (on a curtain rod, for example), where appropriate, but the nickel has a lighter, less formal feel to me than ORB. I think your style will determine which you choose; both look much more updated than brass, usually.

FWIW, we kept the outside knobs and fixtures shiny brass. It seems like a more timeless look on the outside of the house vs on the inside. We decided this because we needed magnetic door knockers and kickplates, and brass was the most readily available finish LOL. :-)

I went with ORB knobs, but my hinges are white like my doors and trim. They have some really cool shapes of knobs too! I went with round, but really liked the egg shape too! You can also get a lever/handle instead of a knob.

And even though my door knobs are ORB, my master bath had brushed nickel lighting, faucets and drawer pulls. So I think you can mix in other metal finishes in the less common areas.

I found some GREAT deals on all of the knobs and things on ebay, so definately look there. I think the guy I bought from was door2door?? Not certain, but I can find out if you are interested.

... or you can do what we did and change the knobs to brushed nickel and leave the darned hinges because of the expense to replace! No, I don't recommend it -- it looks pretty stupid if you start to think about it. But I just choked on the cost so we left the hinges. Someday we will change them out ...

We chose ORB when we sold our house last year just because it looked better in the house (1994 Cape) - the only place that had BN was the master bath. Both are "in", some will like BN better and some will like ORB better, so it's pretty much "flip a coin"! We used nice levers for most of the doors simply because I thought they were pretty, but it's also easier to operate a lever if your hands are full, you're wearing mittens, or you have arthritis in your hands or wrists. (If we had gotten the little ranch we had bid on we'd be putting levers on the doors, but there's no way I'm replacing these antique porcelain knobs!) We too purchased our hinges on eBay for 1/4 the cost of the ORB ones at the home centers, and got a great deal on the knobs/levers by purchasing them in a multipack on eBay. They were an unfamiliar brand (Copper Creek?) but I was happily surprised by how sturdy they seemed when they arrived. Do be careful, though, as there are two different ORBs out there - one has a cool, gray tone, while the other is a warm brown. If you order the hardware from anywhere make sure you ask which it is because they look awful together!

I think it looks unfinished if you leave the old brass hinges and just change the knobs out, as a buyer a little part of me would have been wondering just how many other projects had been just half-done? If you have two people to do the job and a cordless drill/screwdriver with a full charge, taking the doors down to change out the hinges is a very easy job even if you're hopelessly unhandy.

I've been making the same changes in our 1995 house. There was brass everywhere- light fixtures, faucets, hinges and knobs. Almost all the brass finish is gone from the faucets and the drains are completely gone. I'm even replacing the visible plumbing pipes behind the pedestal sink. I'm using BN for all the hinges and knobs. (wish I had spent more and got the lever style) Some of my light fixtures will be black/iron/bronze.

But since you are selling - I think brushed nickel is more neutral and will appeal to more buyers.

We are also in the process of doing the same thing. Our house was built in 1996. We have gone with ORB, but in retrospect would have chosen brushed nickel. The ORB is hard to find locally (and I live in a city of almost 1 million people), so I have had to order everything. We have extremely hard water, and the ORB faucets show water spots terribly. Anything is better than that horrible polished brass, though!

I have a 2800 sq. ft. home built in 1995 also. I just replaced all my knobs, door handles and hinges. They were shiny brass and I went with ORB. I think my home has a bit more of an "Old World" style to it, so I liked the idea of the ORB as opposed to brushed nickel. I also purchased the hinges from ebay. (knobs and handles from a big box store)

My DH was able to change the hinges without completely taking the doors off. He just removed one hinge, replaced it and then did the second and then the third.

I prefer ORB, as it seems a little more classic/old school and less Jetsons, plus I think it just "goes" with any style. For example, BN would seem odd in a colonial but ORB might still work in a minimalist modern house. Still, I think it totally depends on the home's style and your style.

Good luck!

another ORB fan here. i did put nickel in the baths that had nickel or chrome faucets at our last house - but in this one stuck with orb everywhere. we have the egg style knobs - got them on ebay too.