One of the most afordable cameras,and one that has low noise across a broad ISO range is the original Canon EOS 5D, the 12.8 megapixel, full-frame model. This camera is available for around $1,000 used,and it puts low demands on the lenses used, is easy to carry, and works very well with Canon lenses, and also with adapters and Nikon or Pentax or Yashica/Contax lenses.
Nikon makes some superb wide-angle lenses that are better than Canon's wide angle prime lenses. Sorry, but it's true. Lens quality is a big factor in quality images. So is use of a tripod and good focusing and good camera technique.
A high-quality 5D image,shot with a *quality* lens, from a tripod-mounted camera, can be up-sampled quite well, negating the need for a $6995 to $8,000 high-rez Canon or Nikon D3x body. With the ultra-high MP counts in the 21 to 24.5 MP category, the slightest bit of camera shake, the slightest bit of missed focus, the slightest bit of subject motion blur, and all the extra MP goes right out the window.
12 to 13 megapixels on full frame is about the limit for hand-holdable pictures for many shooters. Camera stability, focus,and lack of vibration/movement begin to be *huge* factors at 12 to 13MP. You might just as well sink $500 into a tripod and head now, because without a quality tripod and head, your money just goes down the toilet above 12-13 MP.