Take a look at the shots by Valou, here nickname valouchufy.  She uses a Nikon D50.  Excellent images. Then again, she is a talented lady with a good eye.  A coworker of mine also uses the D50 with excellent results.

I use both D70 and D200.  The D70 is my "carrry with me" camera.   My lenses include some Nikon and an assortment of Sigma. The Sigma to me do a credible job, sticking with the better ones and not the low end.  The same is with Nikon.  I cannot afford a bunch of Nikkor optics..so Sigma offers and provides me a good option.

The only problem with Nikon at the moment is supply.  Sure, if you loose a cover of some sort, like I did on the D200, they sent me a new one no charge.  Still, production is not up to speed and some items are backordered for a while.   

Overall, I cannot comment on other makes since Nikon is what I use in digital and in the previous film camera.  My wife uses a Pentax 35mm, not a slr model.

I wish you the best with this.  You might try also Hunts Photo as well as Adorama.  There is also a site for Sigma lenses, Sigma4Less or something like that.  They do other brands "4less" but as with Adorama and Hunts are reliable and provide good service.

TomD'Art.

PS. Digital SLR is not a big deal.  Sure, it needs a computer.  Editing in a digital darkroom is both fun and very versatile.  I don't think the change will take much getting used to, especially since you have shot digital already and have some experience there.  The DSLR reopens the SLR world again but in a different format.
As for memory, get more than one. I never like putting all the eggs in one basket.
Even a 512 will give decent amount of Fine .jpg with 6mg images.  A gig is what I like and have a few.  For the D200 I choose the larger cards since most shots are in raw.