multichannel DAC project from PC

[cougarz]

Hello to everybody.
I'm planning to use in my multi-amplified 3 way speakers a MOTU ULTRALITE as multichannel preamplifier and DAC. I love oc audio sound and flexybility (digital equalization and time optimisation by VST plugins) and i was wandering if there is a DIY way to achieve equal or better results.
My budget is the price of MOTU, around 500€. I need 6 mono channels (ie.e 3 stereo ch.)
My idea is:
USB->I2S multichannel converter
3 stereo DAC I2s->analog
solid state 6 ch preamplifier

Obviously i can't afford really hi-end stuff. There are a lot of things in a multiamplified system (it's used on a car, that's why i can't leave multiamplification, time alignment is fondamental!).
The most important thing is sound significantly better than MOTU soundcard (AKM integrated DACS)
Any suggesstion is apreciated!!
Bye

Paolo