Very useful plugin so far! I'm glad there is an XMPlay only option as well.
Thank you for taking the time.
A few things to note. NSFPlay 2.2 by rainwarrior is known to be the most updated and accurate, open source NSF player known right now. Being that there is a lot of NSF composition these days it pays to be very accurate in playing. Perhaps adding his code would help. http://rainwarrior.ca/projects/nsfplay/
Something very exciting that I would like to add is that the creator of NSF and SGC has created the SPC2 (or SP2) format. (This is also the first public announcement with the resources.)
Here is the spec: http://blog.kevtris.org/blogfiles/spc2_file_specification_v1.txt
The goal of the format was to allow a multiple track set of SPCs in one file that is able to be played on hardware without taking up a lot of ROM space. kevtris, marshallh, and CaitSith2 achieved this.
marshallh and CaitSith2 made an easy to use SPC2 packer (with source): https://dl.dropbox.com/u/36071551/spc2_pack.zip
And here is a 150MB archive of SP2s: https://dl.dropbox.com/u/36071551/spc2.rar
Hope you'll consider supporting this.