To duplicate a high quality full duplex speakerphone look at the Polycom integrated phones. Frankly, in a home office setting you'll only use the speakerphone when on hold or dialing into a call - if you are the only person in your office it's kinda rude to use a speakerphone when you can use a headset (IMHO).
To get an idea of options of types of phones and great quality headsets, check out
www.hellodirect.com. I have one of their reasonable headsets that I use on my cell phone (which is my home office phone).
Don