Menneisyys, great review.
The latest version of gsplayer that supports midi with a plugin is version 2.25 and was just released on Aug 5, 2006 and is available at the author's website:
http://hp.vector.co.jp/authors/VA032810/
I've been playing with this player and it works quite well. Since it's a timidity based player, all the Gravis Ultrasound Patch format patches work with it, so one can build a better patch set than the one that is supplied. (Yeah, I'm one of those original Gravis Ultrasound owners... sbos rulez and logarithmic midi volume control sucks!)
I've grabbed the timidity patch sets from:
http://decwarch.free.fr/audio.html#TIMI
and made a simple GM patch set similar to the GM patch set supplied by Y. Nagamidori. (The timidity patch set includes alot of other non-gm patches and the configuration file is quite snarly.) With these patches, MIDI files sound better... but unfortunately the patch set is just over 16 Megabytes!
The Timidity patch set took quite a bit of massaging to get it into a simple package, so doing it yourself will take a few hours.
I've also used the freepats patch set from:
http://freepats.opensrc.org/
to make a GM set. This is a really nice patch set, unfortunately it's still missing quite a few GM patches. So I filled the missing patches with ones from the timidity. This one works out to approximately 34 Megabytes! The freepats patch set works pretty much out of the zip file with gsplayer with minimal tweaking of the crude.cfg file (which fills its missing patches by duping GM assignments with existing patches.) The missing patches sourced from the timidity patch set take up approximately 3 Megs.
I'll make my tweaked-for-gsplay patch sets available for download if someone can recommend how I can distribute the files (free file hosting?) The timidity patch set download will be 16 Megs, and the timidity patch-the-holes-in-freepats patch set download will be 3 Megs since you can get the freepats-20060219 zip or tar file (28M or 25M respectively) from freepats.opensrc.org.