Going by what I have seen the main thing is the comfort of the camera while using it. I figure the entry level will be replaced eventually as technology increases. I understand the glass for the lenses is the piece that won't need replacement in the same sense. Do people who upgrade keep their old DSLR cameras for any particular reasons when they upgrade besides maybe a spare? Also if I were to order one online since I am currently in Italy, is there any prefered website or company to ensure the warranty is good. I know not to buy in Italy because the warranty is only for the country of purchase.
Others have given you good general advice. My specific suggestions would be:
Buying new, I would strongly suggest B&H in NYC.
http://www.bhphotovideo.com/
Buying in euros is painful!
As usual, *I* would buy used. For Nikon, go to the "I want to sell" forum at nikonians.org. You can usually use a credit card via PayPal.
For Canon, fredmiranda.com.
Nikon D80 cams, in excellent condition, are going for $400. Get a Tamron 17-50 f2.8 (older non-motorized is slightly better, but either version is fine), $320. Get a sb 600 flash ($150) and you have a VERY solid kit for $870.
If the 17-50 is too much money at this point, find a 18-70 for $160.
Or...buy a new D90 for the same price ($900), body only. Awesome cam.
Or...pick up a D300 for around $1200, body only. If you shoot a lot of action / sports...this is the way to go. Since you don't...the D90 is an excellent choice.
For architecture work, it's HIGHLY likely you will want some wide (-ish) angle lens. Some good choices, Sigma 10-20 or Tokina 12-24. The Tokina would be my choice for a start up kit. The Tamron 17-50 is an awesome value and great general range. These lenses are available in Canon mount as well.
If you prefer Canon's ergonomics, I would suggest looking for a used 40D at fredmiranda's site....very nice cam. Better than the newer 50D imo.
Bag: Kata 3N1-20 (or 3N1-30).
Last bit of advice...get a tripod, BUT...don't buy cheap tripods. They are an utter waste of money. If necessary, save up...then "do it right". It will save you money in the long run.
OK...one more bit of advice....seek information from better photography forums than macrumors.com, where you'll find more pro shooters. DPreview.com can be unpleasant in some ways, but I think you'll find the information far more dependable.
For Nikon shooters:
nikongear.com
nikonians.org
nikoncafe.com
I'll let the Canon shooters supply the latest and greatest alternatives.
Good luck!
PS: Study Light! strobist.com