Good news all:
I found a decoder that works with AAC+ streams for both WMP and TCPMP:
TCPMP:
http://www.rarewares.org/aac.html
For those of you using TCPMP, you'll want the BetaPlayer/TCPMP plugin. I haven't tested any of the other plugins, but I did verify that this one works with AAC+ shoutcast streams.
WMP:
http://www.orban.com/plugin/
Download and install the plugin. When you want to play a stream, open URL:
icyx://XXX.XXX.XXX.XXX:YYYY
Note the ICYX in place of the HTTP. This forces WMP to use the plugin DLL, and still allows you to play regular HTTP streams w/o a plugin, if desired. read the readme for full info.
Enjoy!
-ben