My '99 Legacy 2.5GT 5 speed sedan weighed in at 3250# with me (about 190#) at the dragstrip scale. I think the gas tank was pretty empty, so add another 100# or so for a full tank of gas. Also, isn't the Limited automatic only? If so, add a bit more for that, too. Now that I think of it, I believe the owner's manual has weight specs for all the different models, so you could check there.
As for brake upgrades, unless you want to spend and arm and a leg there's not too much you can do. A guy with an Impreza just had Wilwood calipers installed up front, and I think he may have moved his stock calipers to the rear - do a search of the General and Technical forums for "Wilwood" and you should find the post.
As for my car, my first brake mods were Mintex 1155 pads and Goodridge SS brake lines (car had about 22k miles at the time, so stock stuff was still in good shape). The Mintex pads made a HUGE difference - excellent bite, cold or hot, wet or dry. VERY dusty, though, and sometimes squeaky at low speeds. Since I had the pads and lines done at the same time, it's tough for me to say if the SS lines made any real difference, but supposedly they help to maintain pedal feel as the car ages.
My next modification (perhaps this weekend) will be the installation of some new front rotors. My stock rotors now have about 26.5k miles on them and are pretty badly warped. When I had the new pads installed, the rotors were turned and the guy told me they didn't have enough material in them for another turning, so I went for new rotors. Anyway, the rotors have been cryogenically treated, which makes them stronger, more resistant to warping, and longer lasting. Check out www.frozenrotors.com
for more information.
I talked to Mark at Diversified Cryogenics - he and I agreed that although slotting looks cool, I just don't need it for street/auto-x/sporadic open track duty. Slotting would have cost about $90 extra I think. As it is, I got OEM Subaru rotors treated and shipped for $274 - pretty expensive, but I've gotten word from a few different sources that cryo treating really works, so I think it will be worth it.
'99 Legacy 2.5GT 5 speed sedan