Getting an accurate print at our lo tech office

I work at a building company in VT an have recently been printing images of our work for a variety of reasons. I am constantly making adjustments to my images as they make their way from the digital camera to the computer through several programs, and out the printer. I have printed the same picture on our three office grade printers (Epson C82, hp sc 2175, and hp officejet r 80) and they each look totally different. One even lost a quarter inch in length over a six inch distance!
I am printing 300 dpi tifs cmyk. I have tried to calibrate my mac g4 screen to the epson, and it just looks like crap. I make sure all the printer output settings are correct. I am trying to generate high quality prints for very limited use (accurate mock-ups, nice photos for portfolios shots), not for bulk printing.
I don’t know where I should concentrate my efforts in order to get nice prints. Any advice? What is a step up from these printers? Is there a $1000 printer that can be driven by a mac and a pc? What the hell is SWOP? Do I trust my computer to “Color manage” ? When I’m putting together a project, can I switch to cmyk mode from rgb without deteriorating the image? Does it matter if rgb images mix with cmyk images on a project, then switch the whole thing to cmyk at the end?

Thank you for any help on this confusing matter.
Here is our site, if you are interested. I just built it.