There are a few phones that do almost all of those things. The HTC Wizard sold as the Cingular 8125 and T-mobile MDA do everything except the A2DP. The MDA may do A2DP with a rom upgrade.
The wizard will do internet over GPRS, Wifi, and with Windows Mobile 5 software it has somewhat limited MS Windows functionality. Word, Excel, and Media Player. And you can install programs on the device that have more functionality.

Hi.. i'm interested in purchasing a smartphone but there are certain functions that i need on the smartphone but i couldn't get much details out of websites so i'm asking you all's help...
here are things that i need

bluetooth stereo profile (A2DP)
wi-fi
internet (access to hotmail and msn messenger will be sufficient)
media playback ( i don't know if there are any phones that support .avi files but that would be nice)
and most importantly word document editing capability (if not at least somethere where i can type in text document and view it later on a computer)

i'm wondering if there's smartphones that does all this but please advice on this matter.. i really appreciate it.. thank you