Not only do I do computer graphic arts, but I also am a network administration and PC specialist. I own all three brands HP, Epson & Canon. I personally have never been very happy with any of the color HPs I've owned (they make the best bw lasers, though). I think HP is good at marketing and that's why they are so popular. HP has the largest droplet size; Epson's and Canon's droplet size are identical and are significantly smaller. DPI no longer means anything, its the size of the droplet that determines the quality of your photos. My best results have been on the Canon and I have been a die hard Epson fan.
Most commmerical photo plants use the high-end Epson (the ink is identical to the archival ink sold to consumers). However, when you use a good quality paper with a high clay content (I seem to get the best results with Kodak Professional, Epson Professional & Avery's papers (all retail consumer papers)...and I've tried them all) and I get stunning results on the Canon. I also get fabulous results on the commercial papers I use.
I touch-up action photography and people think that I took the film (from my digital only camera) and had it developed at a commercial plant. I produced one photo from a 72 dpi downloaded image (to use as a color proof) that a professional sports photographer thought I had taken on my camera and had printed digitally.
One bad thing about all these new printers is that even with the 6-8 cartridges you go through a
LOT of ink. So if you print a lot of pictures it gets expensive. Check with your local commercial photographers if you know one. I have a friend that orders my ink for me at significantly reduced rate through a place that will only sell to licensed, professional photographers.
The other thing needed really fantastic photos is to make sure that every item of hardware you use (scanner, monitor, printer) and color calibrated for AdobeRGB1998. This will help ensure (but not guarantee) that what you see is closer to what you get. One other important point, when you go shopping for a printer ignore the picture samples that you can get off the printers at the store. The photos are specifically selected to make the printer appear at it's best in flourescent lighting. Ask if you can bring in a photo on a CD and print it on each of the printers you are looking at so you can make an accurate comparision. My local CompUSA has been very accommodating about this even allowing me to calibrate the equipment properly.
Hope this helps.