I am sure you will get many different answers for this post but here are my thoughts: I have 7 Dell computers. The one in my scrap room is 6 years old and still working fine. I could switch to one of my newer ones but why it works so well with my Pazzle Inspiration. I have 4 HP printers and one large format Epson in my home. I mainly use the Epson for scrapbooking, not digital scrapping, just printing clip art and journaling. I am still waiting for an "actual" photo printer, however my HP's don't do too bad even though that is not what they were made for. Just make sure you get a printer with individual color cartridges.
Probably any number of computers would be fine...depends on your budget and what else you would like to do with it...are you computer savvy?
I would say the most important thing for printing pictures is to invest in a good photo printer...I did a bit of research on photo printers before I bought mine...we already had an all-in-one printer...
I purchased an HP Photosmart Premium C310...it was one of the highest rated ones (but there are others) and works beautifully!
I don't think they sell printers with combined colours anymore....they pretty much all have separate ink cartridges....try and get one with the two different blacks (printing black and a photo black) plus the other standard colours. I believe most good photo printers do this.