There is an output plug-in that offers beat matching when crossfading songs, called "SqrSoft Advanced Crossfading Output v1.7.6 for Winamp". Although old, it still works quite well on my system. All such beat matching apps work best when the BPM of consecutive songs are not very far apart.
It may take a few attempts to set it up appropriately for your system. A number of presets are provided. One or more presets must be imported from the "Winamp/Plugins/ACF Presets" folder before one can be selected. This plug-in was last updated in 2008, so there are a few things to watch out for.
1. The configuration file "out_sqr.ini" is written to the "Winamp/Plugins" folder. This is a restricted folder on Win 7, so in order to have any changes to the default settings saved, Winamp needs to be run under Administrator mode for the session(s) in which any changes are made.
2. A control panel is installed that may interfere with some WA skin functions. The control panel file "gen_acf.dll" can be renamed or removed from the "Winamp/Plugins" folder without affecting the main output plug-in file, "out_sqr.dll". The set up options can still be accessed through the "Winamp Preferences - Plug-ins - Output" page.
3. The default sound device selected is the "Microsoft Sound Mapper". Your sound card/chip may also be selected. See item 1 above if you want to save this change.
4. The output will follow the bit depth and sampling rate (no greater than 16 bit@48KHz) and channels (mono or stereo) of the source file when set to auto (default). The output may also be set a particular bit depth, sampling rate, and mono or stereo channel setting.
Those with a multichannel speaker setup will need to use their sound card/chip up-mix utility or the Windows "speaker fill" feature to get sound on all of their speakers (assuming your sound card/chip driver supports this).
Upsampling beyond 16 bit@48KHz, if desired, would also have to be supported external to this plug-in. Win 7 (and Vista) provides upsampling in shared mode (controlled through the Windows sound control panel) if your sound card/chip driver supports higher bit depth and/or sampling rates.
It should be noted that Windows will also provide mixed sampling in shared mode, i.e. if the SqrSoft ACF plug-in is set to 16 bit@48KHz and Windows is set to 16 firstname.lastname@example.orgKHz or 24 email@example.comKHz or 16 bit@96KHz or 24bit@96KHz, then the output to the sound card/chip will be 16 firstname.lastname@example.orgKHz or 24 email@example.comKHz or 16 bit@96Hz or 24bit@96KHz.
The default WA output plug-ins and this one work in shared mode.