y exactly do you want one? they are going to do exactly the same thing as routing out from your sequencer.
when you set up an aux channel on your sequencer and route individual tracks to it you can still process those tracks seperatly. you also have the added advantage of processing them as a group if you like (ie drum group compression)
i think you're looking too hard at what is a very simple solution. the more variables you add the more chances to get things wrong.
keep it simple. you have a good interface and a good desk. dont comprimise the audio signal with crap gear when its not needed. i understand the want to go outboard but going outboard is only an advantage IF you have quality outboard. a quality vst compressor or eq will ALWAYS sound better than a cheap outboard one.
try think outside the box on this. remember up to fairly recently we all had to bounce tracks to make more room for other tracks on a desk - a true analogue desk is limited in channel count anyway. you have firewire to your desk and a seperate interface. sit down with a pen and paper & draw out differant routing configurations and try figure out the best way to make the most of that nice set-up that you have.