With the quality of the well known brands, the main deciding factor really becomes, what feels good in your hands? Get to a quality camera shop and hold each one. Take some sample pictures, mess with the settings. Then go home and read, read, read!! A couple good starting places are:
http://www.fredmiranda.com/
http://photography-on-the.net/forum/
http://www.dpreview.com/
Any of the well known DSLR brand, ie Canon, Nikon, Sony etc, will give you good results, once you learn how to use them. They all have "consumer level," pro-sumer level," and "professional level." Well, at least Canon and Nikon do. Any of these levels will allow you to take great photography. Once you start talking "Macro," you'll need somewhat specialized and expensive lenses. For instance, I shoot Canon. For several years, I shot with a RebelXt and a 100mm Macro lens. I recently upgraded to a Canon 7D body. I still use the 100mm Macro.
Now Canon has several consumer bodies, that offer a lot of the features that the higher end bodies offer, such as the Canon T2i. This would be a great "starter" DSLR camera, while still offering you a lot of the features that the "prosumer" bodies offer, for around $750.00 (body only). Unfortunately, even if you find a great deal, on a used 100mm Macro lens, you're still looking at spending $400.00. However, it's well worth the investment. The 100mm Macro is also a great portraiture lens.
If it were me, keeping my budget within $1000.00, I would look for a used Canon 40D (better than the newer 50D IMO) with a variable zoom lens, for around $600.00. Then I'd keep my eye out for a used 100mm Macro.
Another option would be a Canon T1i kit, with an 18-55IS lens, for $800.00
http://www.onecall.com/product/Canon/EOS-Rebel-T1i-w-EF-S-18-55mm-IS/Digital-SLR/_/R-96621
or
a Canon T2i kit with the same lens, for about $900.00
http://www.onecall.com/product/Canon/EOS-Rebel-T2i-Kit/Digital-SLR/_/R-103342
These are both great consumer grade DSLR cameras, with the main difference being in the megapixels. No one needs 18mp anyway...lol.
Either way, you'll still need to save up a bit more money, before purchasing a Canon 100mm Macro. Canon's newest 100mm Macro includes Image Stabilization (IS) and is an L series (professional series) and runs about $950.00. The non IS version, which I shoot with, and is still an amazing lens, though not L or IS, and runs about $500.00 new. Now that the L, IS version has been released, the older versions are much easier to find, used. With a little looking, you could find a used one for $350.00. They do hold their value, quite well.