Not a fan of large zooms. I would actually recommend going wide with a 16-35 and then long with a 70-200. Then you'll have your 50 in the middle. If you cannot afford it all at once then build up slowly. I wouldn't waste the money on a mega-zoom with a variable aperture.
The 50 1.8D in my experience is a bit soft wide open. There is a new 50 1.8G being released next month, hold out for that one.
Well, I'm planning on selling the 18-55/55-200 to fund new lenses. Although I wouldn't be able to fetch much more than $100 for the 18/55, so it might be worth keeping.
I'm stuck on versatility, as a lot of my shooting tends to be just throughout the day, messing around with friends, hiking, etc. And changing lenses in those situation will be just a giant pain in the arse, can you see why the "meg-zooms" appeal?
But further research is starting to tell me exactly that, mega-zoom lenses aren't exactly a good choice... My biggest issue is cost, followed closely by needing a versatile lens...
As for the new 50, I hadn't heard that, and I was unaware of the pending new release. I imagine the new lens will be substantially more expensive?
I, like you, am in university, so I get the bit on costs. If I were you, I'd look at purchasing the 50 for portraiture, but TBH, it sounds, ,for more of your needs, the 35mm 1.8 is a better choice. With cars, you want something wider, generally, so you can get it with the 18-55, but the 35mm is going to be a lot sharper and better with color. You sound like you want to shoot all kinds of things, which isn't very budget friendly ("everything else"?), but, fortunately, none of the top ones have to have a lens with super fast AF. The Tamron and the Nikon are not very different in terms of AF speed that it'll make a significant difference for you I don't think.
I started with a D40 + 18-55mm in the summer of '09. Right away, as a college student, I knew I had to get paying gigs to support what I wanted; better equipment. I bought a 50mm 1.8 (which I still have), and did a ton of portraits. Everywhere. All the time. It was all about versatility for me, which, from the looks of it, doesn't sound like a 50, but the ability to control the DOF that much made such a difference. The next bit of kit were cheap flashes (Vivitar 285HV's), and I was really able to push my photography. There's not much you can't do with a DSLR, 50mm 1.8, and a couple of vivitars. That said, if you push yourself, and you're a little crazy, you can end up with a typical college kid $2000 car with $30,000 worth of equipment in it
I was actually just looking at the 35mm f/1.8. Both the 35 and the 50 only have a 44* max viewing angle. Is that really that "wide"? My 18-55 is capable of a 71* angle at 18mm. Also, I can't do with the inability to auto-focus with the 50 on my D60, so as of now it's out of the question, although apparently there is a new 50 being released soon, possibly with the ability to autofocus on my body?
Also looking at flashes, eventually I'd like to pick up the SB600 or SB700, definitely in the future!
The more I research, the more difficult it is becoming to decide on a lense!
Your subjects are so wide you need all the major lenses really - wide, standard, zoom, macro. I think you need to tell us what you mostly shoot, or mostly want to shoot, rather than "everything".
What does your current equipment not do that you need it to do?
I know, I know, but all photographers run into the same problem do they not? The top three of my list, are definitely the three subjects most commonly shot.
My current equipment "does" everything, all the clarity/sharpness of my automotive photography is definitely lacking... I just want to do everything better 
