gonna necro because i went through most of these particles recently and found the few usable ones for anyone interested.
"versus_door_slam"
sparks and a little smoke. looks like a regular explosion without the initial flash. can be a little bit hard to see at times.
"crate_drop"
puff of smoke with some debris. animation lingers a few frames too long so i am not a fan but it looks neat.
"mvm_loot_coreflash"
this is my second favorite. white flash that looks a bit like the sunbeams unusual effect. very non-distracting but still looks like an explosion.
"mvm_loot_explosion"
cool explosion effect with white smoke and sparks but definitely larger than regular explosions and a bit harder to see through
"taunt_demo_nuke_explosion_flash"
looks like the default explosion flash with no debris or smoke. rather nice.
"taunt_demo_nuke_explosion"
my personal favorite. small orange explosion with no debris or smoke. about 60% the size of default explosions.
"merasmus_bomb_explosion_blast"
cool looking explosion but it is green so it looks funny.
the default explosions are too distracting for me in DX9, (fine in DX8) but the spy sapper effects and other small explosion options just look bad in my opinion so if anyone has other effects they like let me know pls. these were the best i could find.