Man, that ECHO 2 looks fine. With the DMP and that speck, you shouldn't need any preamps on your interface, as you'd have to spend a lot more on an interface to get one with preamps that sound better than what you have.
One thing to keep in mind is what size Firewire input you have on your laptop. I might be getting the numbers wrong here, but I believe they come in four-pin and six-pin, and that the Echo has a six-pin output. A lot of laptops have only a four-pin input. You can get a cable that goes from six pin to four pin, but the interface won't be powered through the firewire cable and you'll have to use a wall wart with it. Not a huge problem, but something to keep in mind.
With the outboard gear you've got, all you really need in an interface is the best quality AD/DA conversion you can afford. That ECHO 2 really does look like your best bet.