The Adventures of Duane & BrandO (VG rap with rocking backing music, I'm sure you know them though)
Akineko (Japanese, mostly Square but some other good stuff too)
ansgaros (more heavy metal style, really well done remixes, almost Sixto level)
Armcannon (a supergroup made up of some of the best VG remixers period)
Artificial Fear aka Mat Graham (lots of Zelda remixes)
Ashane (some of the best Chrono Trigger remixes and some other good stuff)
BrainCells (a few really good remixes, fast paced metal)
CarboHydroM (a ton of excellent remixes from lots of different games including THE best Zelda remix period, almost Sixto level)
Daniel Alm (some really solid remixes from a variety of games)
Danimal Cannon (the lead guitarist of Armcannon, has some great solo stuff)
Darangen (a bunch of solid Square and Lufia remixes)
Divine Wrath (if you like Cave Story)
Dr. Manhattan (some really great remixes from some generally more obscure games)
FamilyJules7x (a ton of N64 game medleys and Pokemon music)
goat (THE best and most thorough remixer of Castlevania music period, also some other games)
OA aka Hope Fails (a few really great remixes from generally more obscure games)
housethegrate (a few amazing remixes, almost Sixto level)
Joren de Bruin (a few really great remixes)
Kidd Cabbage (some solid remixes from mainstream games)
LEAF EXCEED Music Division (some solid remixes from various games, mostly Cave Story)
LuIzA (some great metal remixes)
M-H (a ridiculous amount of solid remixes from a ton of different games, almost Sixto level though not all his songs are winners)
norg (some solid remixes)
Preludio (a Japanese band with some solid FF remixes)
Prince of Darkness (a bunch of solid remixes from various games including a fantastic Mega Man X medley)
Project Scytia (a Japanese band with a bunch of solid Chrono Trigger and FF remixes)
Sbeast64 (some solid remixes including some of the best DKC remixes I know of)
Sixto Sounds (duh, without a doubt the best video game remixer out there)
The Smash Brothers (a supergroup of well known VG remixers with Ailsean as the lead guitar)
SnappleMan (some really great remixes including a fantastic Chrono Trigger final boss medley)
Stemage (the lead guitarist of Metroid Metal, has a ton of Metroid music he's remixed himself along with a few other games)
Tackle (a few really solid remixes)
VikingGuitar (most of his music is meh but he has a fantastic 11+ minute Mega Man X2 medley)
XMark (a few really great remixes from mainstream games)
Year 200X (some great remixes from mostly mainstream games)
This is just the best stuff not on your list that I can think of. I have almost 4000 VG remixes, about 90% rock/metal. Feel free to take a look whenever you get a chance.