Nikon 17-55 f/2.8 or a 3rd Party Lens (Sigma/Tamron)?

I'm in need of a kinda wide angle lens but not so much, basically just need a lens that can cover large groups and can get tight-superb all around lens.

I was leaning towards a Nikon 17-55mm f/2.8 Lens ($1424 on B&H), now as always I love Nikon superb glasses it's just that they're pretty expensive but worth it. But if the 3rd party lenses (Such as the Tamrom 17-50 f/2.8 or the Sigma equivalent, forgot their version of it) are just as good I would stop my 'Nikon Lens Only Rule' and get the 3rd party version.

If equipment helps, I have a Nikon D7000, Nikon 50mm f/1.8D, and Nikon 70-300mm f/4.5-5.6G AF-S VR IF-ED Lens. So a 17-55 would be a good range of all of mine focal lengths even if the APS-C changes the focal length from my D7000 so a 25-82mm equivalent. I could also save up to get a 14-24mm and not get a 17-55 if that's better suited for large groups and weddings.

In the future of course, i'll get a full-frame body, but for now i'll need to stick with my DX camera.

I usually rent the lenses I need for weddings. As i'm just a student and have no money for the holy trinity of the 3 nikon lenses. Any help/advice is appreciated. Thanks!

Added (1). @proshooter - Much appreciated for your input, I've heard decent amount of reviews for the tamrom 17-50 f/2.8. Thanks!

Added (2). @Keerok - Hi Keerok, the 18-55mm kit lens? The standard kit lens that comes with the D7000 was the 18-105mm. But I don't like that lens so I bought just the body and my 2 other lenses. That link you provided looks nice just cost a lot. But yeah I don't have a 18-55 and it seems cheap but from the reviews it looks reliable. What kinda flash would you recommend?

This is a test comparison between the Nikon kit lens and the Sigma and Tamron 17-50mm lenses.

http://aviewfinderdarkly.com.au/2011/08/30/three-way-standard-zoom-lens-review/

I have the Tamron 17-50 f2.8 and it is a good value flexible lens with a nice wide aperture.

I find it a good lens for candid wedding shots, particularly groups.

Where's your 18-55mm? It's supposed to be great with large group shots. Want the best image quality possible?

http://www.bhphotovideo.com/...F_3_5.html

Weddings? Again, where's your 18-55mm? That's perfect for weddings! You could use your 50mm f/1.8 for critical portraits and everything else from group shots to ceremony to reception can be done with the kit lens. What you'll really need is a huge flash. The DX will earn you lots of money without having to use a full-frame. With weddings in the end, what is important are the prints.

I use a Tamron 17-50/2.8 myself and am very happy with it. The non-VC verrsion is said to be sharper than the VC verison, but that's not true - the VC version has some sample variation regarding backfocus issues. A good one will be just as sharp as the non-VC version.

Anyway, if i were in your shoes (actually, i'm in a very similar situation) i wouldn't even consider the Nikon 17-55/2.8.It's $1400 for a DX lens after all. The Tamron will offer 95% of its performance at a third of the price, and you won't be able to either of these lenses properly when you upgrade to full frame.
I'd strongly suggest getting either the Tamron for as long as you use DX cameras, or going straight to the stellar Nikkor 24-70/2.8 which you will likely need on the long run anyway. *drools*

It's just $400 more expensive than the Nikkor 17-55/2.8, will work perfectly on full frame and is another step up in quality.
24mm at the wide end should be sufficient for group shots even on DX cameras.

Rent it first. The nikon 17-55 is really nice but may not be worht the money. A tamron 17-50 is almost as good and still leaves you cash for a flash or two. Nikon only for that!