Cool, I'm personally a Galaga fan. Something about sacrificing your ship to rescue it again and have dual ships just tickles my fancy. I went through the Marketplace and didn't find any other good 400msp Arcade games.
I'm looking for games under 400msp too. Yeah Bloody Good Time is pretty fun. Also try the trials for 3D Ultra Minigolf Adventures, Brain Challenge, and Chime. There are also some classic games that are 400msp: Wolfenstein 3D, Street Fighter II: Hyper fighting,
and Worms . Not much to choose from, these are the ones I'm thinking about purchasing. Most decent Live Arcade games are 800msp and up. If I still can't decide, I might get some cheap Indie games or I might splurge and buy 800 more msp to get Comic Jumper
which I really want.